POSIX(3perl)
✨ NAME ✨
POSIX — the Perl interface to IEEE Std 1003.1, bestie 💅
(this is the POSIX(3perl) page from the Perl Programmers Reference Guide, and yes we're reading the whole thing together, no skimming 🙈)
🎀 SYNOPSIS 🎀
okay so here's the vibe upfront, copy-paste energy fr fr:
use POSIX ();
use POSIX qw(setsid);
use POSIX qw(:errno_h :fcntl_h);
printf "EINTR is %d\n", EINTR;
my $sess_id = POSIX::setsid();
my $fd = POSIX::open($path, O_CREAT|O_EXCL|O_WRONLY, 0644);
# note: that's a filedescriptor, *NOT* a filehandlethat last comment is doing SO much heavy lifting, bestie — it's a filedescriptor, not a filehandle. do not come for me. 🫶
🌸 DESCRIPTION 🌸
so the POSIX module lets you access all (or nearly all) of the standard POSIX 1003.1 identifiers. many of those identifiers have been given Perl-ish interfaces, because obviously we're not gonna do things the C way in this house. ✨
this document gives a condensed list of the features available in the POSIX module. for general info on most of these features, go consult your operating system's manpages, okay? and for functions that are noted as being identical or almost identical to Perl's builtin functions, go consult perlfunc.
the structure is giving organized:
- the first section describes POSIX functions from the 1003.1 specification.
- the second section describes some classes for signal objects, TTY objects, and other miscellaneous objects.
- the remaining sections list various constants and macros in an organization which roughly follows IEEE Std 1003.1b-1993.
also, the notation [C99] marks functions that were added in the ISO/IEC 9899:1999 version of the C language standard. some of those may not be available on your system if it adheres to an earlier standard 😭 and heads up: attempts to use any missing one will result in a fatal runtime error message. not a vibe, but that's the tea.
💀 CAVEATS 💀
bestie. sit down. 🍓
Everything is exported by default (with a handful of exceptions). this is an unfortunate backwards compatibility feature and its use is strongly discouraged. like, so discouraged. so either:
- prevent the exporting (by saying
use POSIX ();, as usual) and then use fully qualified names (e.g.POSIX::SEEK_END), or - give an explicit import list.
if you do neither and opt for the default (as in use POSIX;), you will import hundreds and hundreds of symbols into your namespace. your namespace will simply be full. no cap. 😭
a few functions are not implemented because they are C specific. if you attempt to call these, they will print a message telling you that they aren't implemented, and suggest using the Perl equivalent, should one exist. for example, trying to access the setjmp() call will elicit the message "setjmp() is C-specific: use eval {} instead".
furthermore, some evil vendors will claim 1003.1 compliance, but in fact are not so: they will not pass the PCTS (POSIX Compliance Test Suites). 💀 for example, one vendor may not defineEDEADLK, or the semantics of the errno values set byopen(2)might not be quite right. Perl does not attempt to verify POSIX compliance. that means you can currently successfully sayuse POSIX, and then later in your program you find that your vendor has been lax and there's no usableICANONmacro after all. this could be construed to be a bug. iconic of them, honestly.
👑 FUNCTIONS 👑
one function at a time, alphabetically, we're so organized:
_exit
This is identical to the C function _exit(). it exits the program immediately, which means among other things buffered I/O is not flushed. 😳
Note that when using threads and in Linux this is not a good way to exit a thread because in Linux processes and threads are kind of the same thing (Note: while this is the situation in early 2003 there are projects under way to have threads with more POSIXly semantics in Linux). if you want not to return from a thread, detach the thread.
abort
This is identical to the C function abort(). it terminates the process with a SIGABRT signal unless caught by a signal handler or if the handler does not return normally (it e.g. does a longjmp).
abs
This is identical to Perl's builtin abs() function, returning the absolute value of its numerical argument — except that POSIX::abs() must be provided an explicit value (rather than relying on an implicit $_):
$absolute_value = POSIX::abs(42); # good
$absolute_value = POSIX::abs(); # throws exceptionaccess
Determines the accessibility of a file. 🕵️
if( POSIX::access( "/", &POSIX::R_OK ) ){
print "have read permission\n";
}Returns undef on failure. Note: do not use access() for security purposes. between the access() call and the operation you are preparing for, the permissions might change: a classic race condition. 💀
acos
This is identical to the C function acos(), returning the arcus cosine of its numerical argument. see also Math::Trig.
acosh
This is identical to the C function acosh(), returning the hyperbolic arcus cosine of its numerical argument [C99]. see also Math::Trig. Added in Perl v5.22. ✨
alarm
This is identical to Perl's builtin alarm() function, either for arming or disarming the SIGARLM timer — except that POSIX::alarm() must be provided an explicit value (rather than relying on an implicit $_):
POSIX::alarm(3) # good
POSIX::alarm() # throws exceptionasctime
This is identical to the C function asctime(). it returns a string of the form
"Fri Jun 2 18:22:13 2000\n\0"and it is called thusly
$asctime = asctime($sec, $min, $hour, $mday, $mon,
$year, $wday, $yday, $isdst);the $mon is zero-based: January equals 0. the $year is 1900-based: 2001 equals 101. $wday and $yday default to zero (and are usually ignored anyway), and $isdst defaults to -1.
Note the result is always in English. use strftime instead to get a result suitable for the current locale — that function's %c format yields the locale's preferred representation. 🌈
asin
This is identical to the C function asin(), returning the arcus sine of its numerical argument. see also Math::Trig.
asinh
This is identical to the C function asinh(), returning the hyperbolic arcus sine of its numerical argument [C99]. see also Math::Trig. Added in Perl v5.22. ✨
assert
Unimplemented, but you can use die in perlfunc and the Carp module to achieve similar things. 🙈
atan
This is identical to the C function atan(), returning the arcus tangent of its numerical argument. see also Math::Trig.
atanh
This is identical to the C function atanh(), returning the hyperbolic arcus tangent of its numerical argument [C99]. see also Math::Trig. Added in Perl v5.22. ✨
atan2
This is identical to Perl's builtin atan2() function, returning the arcus tangent defined by its two numerical arguments, the y coordinate and the x coordinate. see also Math::Trig.
atexit
Not implemented. atexit() is C-specific: use END {} instead, see perlmod.
atof
Not implemented. atof() is C-specific. Perl converts strings to numbers transparently. if you need to force a scalar to a number, add a zero to it.
atoi
Not implemented. atoi() is C-specific. Perl converts strings to numbers transparently. if you need to force a scalar to a number, add a zero to it. if you need to have just the integer part, see "int" in perlfunc.
atol
Not implemented. atol() is C-specific. Perl converts strings to numbers transparently. if you need to force a scalar to a number, add a zero to it. if you need to have just the integer part, see "int" in perlfunc.
bsearch
bsearch() not supplied. for doing binary search on wordlists, see Search::Dict. 🔍
calloc
Not implemented. calloc() is C-specific. Perl does memory management transparently. 🧚
cbrt
The cube root [C99]. Added in Perl v5.22. ✨
ceil
This is identical to the C function ceil(), returning the smallest integer value greater than or equal to the given numerical argument.
chdir
This is identical to Perl's builtin chdir() function, allowing one to change the working (default) directory — see "chdir" in perlfunc — with the exception that POSIX::chdir() must be provided an explicit value (rather than relying on an implicit $_):
$rv = POSIX::chdir('path/to/dir'); # good
$rv = POSIX::chdir(); # throws exceptionchmod
This is identical to Perl's builtin chmod() function, allowing one to change file and directory permissions — see "chmod" in perlfunc — with the exception that POSIX::chmod() can only change one file at a time (rather than a list of files):
$c = chmod 0664, $file1, $file2; # good
$c = POSIX::chmod 0664, $file1; # throws exception
$c = POSIX::chmod 0664, $file1, $file2; # throws exceptionas with the built-in chmod(), $file may be a filename or a file handle. 💅
chown
This is identical to Perl's builtin chown() function, allowing one to change file and directory owners and groups, see "chown" in perlfunc.
clearerr
Not implemented. use the method IO::Handle::clearerr() instead, to reset the error state (if any) and EOF state (if any) of the given stream.
clock
This is identical to the C function clock(), returning the amount of spent processor time in microseconds. ⏱️
close
Close the file. this uses file descriptors such as those obtained by calling POSIX::open.
$fd = POSIX::open( "foo", &POSIX::O_RDONLY );
POSIX::close( $fd );Returns undef on failure.
see also "close" in perlfunc.
closedir
This is identical to Perl's builtin closedir() function for closing a directory handle, see "closedir" in perlfunc.
cos
This is identical to Perl's builtin cos() function for returning the cosine of its numerical argument — except that POSIX::cos() must be provided with an explicit value (rather than relying on an implicit $_):
$cosine = POSIX::cos(3); # good
$cosine = POSIX::cos(); # throws exceptionsee "cos" in perlfunc; see also Math::Trig.
cosh
This is identical to the C function cosh(), for returning the hyperbolic cosine of its numeric argument. see also Math::Trig.
copysign
Returns x but with the sign of y [C99]. Added in Perl v5.22. ✨
$x_with_sign_of_y = POSIX::copysign($x, $y);see also "signbit".
🌟 creat
Spins up a brand-new file for you, bestie. It hands back a file descriptor exactly like the ones POSIX::open returns, and when you're done you close it with POSIX::close. Don't ghost your file descriptors, that's so not it 💅
$fd = POSIX::creat( "foo", 0611 );
POSIX::close( $fd );Also go look at sysopen in perlfunc and its O_CREAT flag, iykyk 🎀
🖥️ ctermid
Generates the path name for the controlling terminal. That's the whole job, she's simple and she's thriving ✨
$path = POSIX::ctermid();⏰ ctime
Literally identical to the C function ctime(), and it's equivalent to asctime(localtime(...)). Go read asctime and localtime if you want the lore 💜
👤 cuserid [POSIX.1-1988]
Grabs the login name of the owner of the current process. Cute, right? 🫶
$name = POSIX::cuserid();⚠️ Heads up bestie: this function has not been specified by POSIX since 1990 and is hanging around purely for backwards compatibility. New code should use getlogin() instead. She's iconic but she's retired 💀
⌛ difftime
Identical to the C function difftime(). It returns the time difference (in seconds) between two times, the kind you get back from time(). Go see time 🌸
➗ div
Not implemented. div() is C-specific, so like… use int in perlfunc on the usual / division and the modulus % instead. We do it differently here, periodt 💅
📎 dup
Similar to the C function dup(), for duplicating a file descriptor. It works with file descriptors such as those you get from calling POSIX::open.
Returns undef on failure 🫠
📎📎 dup2
Similar to the C function dup2(), for duplicating a file descriptor onto another known file descriptor. Also uses file descriptors such as those obtained by calling POSIX::open.
Returns undef on failure 😭
📈 erf
The error function [C99]. Added in Perl v5.22 ✨
📉 erfc
The complementary error function [C99]. Added in Perl v5.22 ✨
🚨 errno
Returns the value of errno, no cap.
$errno = POSIX::errno();This is identical to the numerical values of $! — go check "$ERRNO" in perlvar 💜
🚫 execl
Not implemented. execl() is C-specific, see exec in perlfunc.
🚫 execle
Not implemented. execle() is C-specific, see exec in perlfunc.
🚫 execlp
Not implemented. execlp() is C-specific, see exec in perlfunc.
🚫 execv
Not implemented. execv() is C-specific, see exec in perlfunc.
🚫 execve
Not implemented. execve() is C-specific, see exec in perlfunc.
🚫 execvp
Not implemented. execvp() is C-specific, see exec in perlfunc.
🚪 exit
Identical to Perl's builtin exit() function for exiting the program. Go see exit in perlfunc 👑
🌱 exp
Identical to Perl's builtin exp() function — it returns the exponent (e-based) of the numerical argument. But here's the catch, bestie: POSIX::exp() must be given an explicit value, it will NOT just vibe off an implicit $_:
$exp = POSIX::exp(3); # good
$exp = POSIX::exp(); # throws exceptionSee exp in perlfunc 💥
🌱➕ expm1
Equivalent to exp(x) - 1, but more precise for small argument values [C99]. Added in Perl v5.22.
See also log1p 🦋
📏 fabs
Identical to Perl's builtin abs() function, returning the absolute value of the numerical argument — except that POSIX::fabs() must be handed an explicit value rather than relying on an implicit $_:
$absolute_value = POSIX::fabs(3); # good
$absolute_value = POSIX::fabs(); # throws exceptionSee abs in perlfunc ✨
🗑️ fclose
Not implemented. Use the method IO::Handle::close() instead, or see close in perlfunc.
🎛️ fcntl
Identical to Perl's builtin fcntl() function, see fcntl in perlfunc.
🗑️ fdopen
Not implemented. Use the method IO::Handle::new_from_fd() instead, or see open in perlfunc.
🗑️ feof
Not implemented. Use the method IO::Handle::eof() instead, or see eof in perlfunc.
🗑️ ferror
Not implemented. Use the method IO::Handle::error() instead.
🗑️ fflush
Not implemented. Use the method IO::Handle::flush() instead. See also "$OUTPUT_AUTOFLUSH" in perlvar 💧
🗑️ fgetc
Not implemented. Use the method IO::Handle::getc() instead, or see read in perlfunc.
🗑️ fgetpos
Not implemented. Use the method IO::Seekable::getpos() instead, or see seek in perlfunc.
🗑️ fgets
Not implemented. Use the method IO::Handle::gets() instead. Similar to <>, also known as readline in perlfunc.
🗑️ fileno
Not implemented. Use the method IO::Handle::fileno() instead, or see fileno in perlfunc.
🏢 floor
Identical to the C function floor(), returning the largest integer value that's less than or equal to the numerical argument. Round down and slay 💅
➖ fdim
"Positive difference": it's x - y if x > y, and zero otherwise [C99]. Added in Perl v5.22 ✨
🎯 fegetround
Returns the current floating point rounding mode, and it's one of these:
FE_TONEAREST FE_TOWARDZERO FE_UPWARD FE_DOWNWARDFE_TONEAREST is like round, and FE_TOWARDZERO is like trunc [C99]. Added in Perl v5.22 🎀
🎯 fesetround
Sets the floating point rounding mode, see fegetround [C99]. Added in Perl v5.22 ✨
✖️➕ fma
The "Fused multiply-add" — that's x * y + z, and it's possibly faster (and less lossy) than doing the explicit two operations [C99]. Added in Perl v5.22.
my $fused = POSIX::fma($x, $y, $z);⬆️ fmax
The maximum of x and y — except when either one is NaN, in which case it returns the other one [C99]. Added in Perl v5.22.
my $max = POSIX::fmax($x, $y);⬇️ fmin
The minimum of x and y — except when either one is NaN, in which case it returns the other one [C99]. Added in Perl v5.22.
my $min = POSIX::fmin($x, $y);🔁 fmod
Identical to the C function fmod().
$r = fmod($x, $y);It returns the remainder $r = $x - $n*$y, where $n = trunc($x/$y). The $r carries the same sign as $x and a magnitude (absolute value) that's less than the magnitude of $y 🧮
🗑️ fopen
Not implemented. Use the method IO::File::open() instead, or see open in perlfunc.
🍴 fork
Identical to Perl's builtin fork() function for duplicating the current process, see fork in perlfunc and perlfork if you are in Windows 👯
📂 fpathconf
Retrieves the value of a configurable limit on a file or directory. This one works with file descriptors such as those you get from calling POSIX::open.
The following will determine the maximum length of the longest allowable pathname on the filesystem that holds /var/foo:
$fd = POSIX::open( "/var/foo", &POSIX::O_RDONLY );
$path_max = POSIX::fpathconf($fd, &POSIX::_PC_PATH_MAX);Returns undef on failure 🫠
🔮 fpclassify
Returns one of these, telling you the class of the argument [C99]:
FP_NORMAL FP_ZERO FP_SUBNORMAL FP_INFINITE FP_NANFP_INFINITE is positive or negative infinity. FP_NAN is not-a-number. FP_SUBNORMAL means subnormal numbers (also known as denormals) — very small numbers with low precision. FP_ZERO is zero. FP_NORMAL is all the rest. Added in Perl v5.22 🌈
🚫 fprintf
Not implemented. fprintf() is C-specific, see printf in perlfunc instead.
🚫 fputc
Not implemented. fputc() is C-specific, see print in perlfunc instead.
🚫 fputs
Not implemented. fputs() is C-specific, see print in perlfunc instead.
🚫 fread
Not implemented. fread() is C-specific, see read in perlfunc instead.
🧠 free
Not implemented. free() is C-specific. Perl does memory management transparently, so you literally never have to worry about it. Iconic behaviour honestly 👑
🚫 freopen
Not implemented. freopen() is C-specific, see open in perlfunc instead.
🔬 frexp
Returns the mantissa and exponent of a floating-point number.
($mantissa, $exponent) = POSIX::frexp( 1.234e56 );🚫 fscanf
Not implemented. fscanf() is C-specific — use <> and regular expressions instead, bestie 💅
🗑️ fseek
Not implemented. Use the method IO::Seekable::seek() instead, or see seek in perlfunc.
🗑️ fsetpos
Not implemented. Use the method IO::Seekable::setpos() instead, or seek "seek" in perlfunc.
📊 fstat
Get file status, girl. This uses file descriptors such as those obtained by calling POSIX::open. The data you get back is identical to the data from Perl's builtin stat function.
$fd = POSIX::open( "foo", &POSIX::O_RDONLY );
@stats = POSIX::fstat( $fd );🗑️ fsync
Not implemented. Use the method IO::Handle::sync() instead.
🗑️ ftell
Not implemented. Use the method IO::Seekable::tell() instead, or see tell in perlfunc.
🚫 fwrite
Not implemented. fwrite() is C-specific, see print in perlfunc instead.
🔤 getc
Identical to Perl's builtin getc() function, see getc in perlfunc.
⌨️ getchar
Returns one character from STDIN. Identical to Perl's getc(), see getc in perlfunc.
📁 getcwd
Returns the name of the current working directory. See also Cwd 💖
👥 getegid
Returns the effective group identifier. Similar to Perl's builtin variable $(, see "$EGID" in perlvar.
🌍 getenv
Returns the value of the specified environment variable. The exact same information is available through the %ENV array.
👤 geteuid
Returns the effective user identifier. Identical to Perl's builtin $> variable, see "$EUID" in perlvar.
👥 getgid
Returns the user's real group identifier. Similar to Perl's builtin variable $), see "$GID" in perlvar.
👥 getgrgid
Identical to Perl's builtin getgrgid() function for returning group entries by group identifiers, see getgrgid in perlfunc.
👥 getgrnam
Identical to Perl's builtin getgrnam() function for returning group entries by group names, see getgrnam in perlfunc.
👯 getgroups
Returns the ids of the user's supplementary groups. Similar to Perl's builtin variable $), see "$GID" in perlvar.
🙋 getlogin
Identical to Perl's builtin getlogin() function for returning the user name associated with the current session, see getlogin in perlfunc.
🧬 getpayload
use POSIX ':nan_payload';
getpayload($var)Okay so this one literally just hands you back the "NaN" payload ✨ Added in Perl v5.24.
Heads up tho bestie, there's an API instability warning over in "setpayload" — go read it before you get attached.
And for the full tea on "NaN", check "nan".
getpgrp
Same energy as Perl's builtin getpgrp() function — it gives you the process group identifier of the current process. See "getpgrp" in perlfunc.
getpid
Returns the process identifier. Identical to Perl's builtin variable $$, see "$PID" in perlvar. 💅
getppid
Identical to Perl's builtin getppid() function, which returns the process identifier of the parent process of the current process. See "getppid" in perlfunc.
getpwnam
Identical to Perl's builtin getpwnam() function — returns user entries by user names. See "getpwnam" in perlfunc.
getpwuid
Identical to Perl's builtin getpwuid() function — returns user entries by user identifiers. See "getpwuid" in perlfunc.
gets
Returns one line from STDIN, similar to <>, also known as the readline() function. See "readline" in perlfunc.
NOTE: if you have C programs that still usegets(), be very afraid 😭 Thegets()function is a source of endless grief because it has no buffer overrun checks. It should never be used. Thefgets()function should be preferred instead.
getuid
Returns the user's identifier. Identical to Perl's builtin $< variable, see "$UID" in perlvar. 🫶
gmtime
Identical to Perl's builtin gmtime() function, for converting seconds since the epoch to a date in Greenwich Mean Time. See "gmtime" in perlfunc.
hypot
Equivalent to sqrt(x * x + y * y) except it's wayyy more stable on very large or very small arguments [C99]. Added in Perl v5.22. 🦋
ilogb
Integer binary logarithm [C99]. Added in Perl v5.22.
For example ilogb(20) is 4, as an integer.
See also "logb".
Inf
The infinity as a constant, periodt:
use POSIX qw(Inf);
my $pos_inf = +Inf; # Or just Inf.
my $neg_inf = -Inf;See also "isinf", and "fpclassify".
isalnum
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:alnum:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
isalpha
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:alpha:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
isatty
Returns a boolean telling you whether the specified filehandle is connected to a tty. Similar to the -t operator, see "-X" in perlfunc.
iscntrl
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:cntrl:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
isdigit
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:digit:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
isfinite
Returns true if the argument is a finite number (that is, not an infinity, or the not-a-number) [C99]. Added in Perl v5.22.
See also "isinf", "isnan", and "fpclassify".
isgraph
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:graph:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
isgreater
(Also isgreaterequal, isless, islessequal, islessgreater, isunordered)
Floating point comparisons which handle the "NaN" [C99]. Added in Perl v5.22.
isinf
Returns true if the argument is an infinity (positive or negative) [C99]. Added in Perl v5.22.
See also "Inf", "isnan", "isfinite", and "fpclassify".
islower
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:lower:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
isnan
Returns true if the argument is "NaN" (not-a-number) [C99]. Added in Perl v5.22. 💀
Note that you can also test for "NaN"-ness with equality operators (== or !=), as in
print "x is not a NaN\n" if $x == $x;since the "NaN" is not equal to anything, including itself. (iconic behaviour honestly)
See also "nan", "NaN", "isinf", and "fpclassify".
isnormal
Returns true if the argument is normal (that is, not a subnormal/denormal, and not an infinity, or a not-a-number) [C99]. Added in Perl v5.22.
See also "isfinite", and "fpclassify".
isprint
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:print:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
ispunct
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:punct:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
issignaling
use POSIX ':nan_payload';
issignaling($var, $payload)Return true if the argument is a signaling NaN. Added in Perl v5.24.
Note the API instability warning in "setpayload".
See "nan" for more discussion about "NaN".
isspace
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:space:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
isupper
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:upper:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
isxdigit
This function has been removed as of Perl v5.24. It was very similar to matching against qr/ ^ [[:xdigit:]]+ $ /x, which you should convert to use instead. See "POSIX Character Classes" in perlrecharclass.
j0, j1, jn, y0, y1, yn
The Bessel function of the first kind of the order zero. ✨
kill
Identical to Perl's builtin kill() function for sending signals to processes (often to terminate them). See "kill" in perlfunc.
labs
Not implemented. (For returning absolute values of long integers.) labs() is C-specific — see "abs" in perlfunc instead.
lchown
Identical to the C function, except the order of arguments is consistent with Perl's builtin chown(), with the added restriction of only one path, not a list of paths. Does the same thing as the chown() function, but changes the owner of a symbolic link instead of the file the symbolic link points to. 💅
POSIX::lchown($uid, $gid, $file_path);ldexp
Identical to the C function ldexp() for multiplying floating point numbers with powers of two.
$x_quadrupled = POSIX::ldexp($x, 2);ldiv
Not implemented. (For computing dividends of long integers.) ldiv() is C-specific — use / and int() instead.
lgamma
The logarithm of the Gamma function [C99]. Added in Perl v5.22.
See also "tgamma".
log1p
Equivalent to log(1 + x), but with more stable results for small argument values [C99]. Added in Perl v5.22. 🍓
log2
Logarithm base two [C99]. Added in Perl v5.22.
See also "expm1".
logb
Integer binary logarithm [C99]. Added in Perl v5.22.
For example logb(20) is 4, as a floating point number.
See also "ilogb".
link
Identical to Perl's builtin link() function for creating hard links into files. See "link" in perlfunc.
localeconv
Get numeric formatting information. Returns a reference to a hash containing the formatting values of the locale that currently underlies the program, regardless of whether or not it is called from within the scope of a use locale. 💖
If you use this function you should also read perllocale, which gives a comprehensive discussion of Perl locale handling, including a whole section devoted to this function.
Warning, bestie: prior to Perl 5.28, or when operating in a non thread-safe environment, it should not be used in a threaded application unless it's certain that the underlying locale isCorPOSIX. This is because it otherwise changes the locale, which globally affects all threads simultaneously. 😭 Windows platforms starting with Visual Studio 2005 are mostly thread-safe, but use of this function in those prior to Visual Studio 2015 can have a race with a thread that has called"switch_to_global_locale" in perlapi.
Here is how to query the database for the de (Deutsch or German) locale.
my $loc = POSIX::setlocale( &POSIX::LC_ALL, "de" );
print "Locale: \"$loc\"\n";
my $lconv = POSIX::localeconv();
foreach my $property (qw(
decimal_point
thousands_sep
grouping
int_curr_symbol
currency_symbol
mon_decimal_point
mon_thousands_sep
mon_grouping
positive_sign
negative_sign
int_frac_digits
frac_digits
p_cs_precedes
p_sep_by_space
n_cs_precedes
n_sep_by_space
p_sign_posn
n_sign_posn
int_p_cs_precedes
int_p_sep_by_space
int_n_cs_precedes
int_n_sep_by_space
int_p_sign_posn
int_n_sign_posn
))
{
printf qq(%s: "%s",\n),
$property, $lconv->{$property};
}okay so the members whose names start with "int_p_" and "int_n_"? Those got added by POSIX.1-2008, so bestie, they're only living on systems that actually support them 💅
and if you get a value of -1 back for one of the numeric entries, that's the universe telling you the field is not applicable to the locale. That's rare, fr fr — mostly it happens in the C locale and its little friends, which just don't have most monetary values defined at all. It can also happen, quirkily, in fields that are otherwise boolean, to signal that the value is kinda neither true nor false 🫠 and that specifically goes down in "p_cs_precedes" and "int_p_cs_precedes" when the currency symbol neither precedes nor succeeds a positive value but is infixed instead, by replacing the radix character.
heads up! Prior to Perl v5.37.7, empty string fields and numeric fields with value -1 were omitted from the returned hash. So if you're on old Perl, don't go looking for a key that isn't there 😭
🌸 "localtime" 🌸
This one is identical to Perl's builtin localtime() function for converting seconds since the epoch to a date — see "localtime" in perlfunc — EXCEPT that POSIX::localtime() must be provided an explicit value (rather than relying on an implicit $_):
@localtime = POSIX::localtime(time); # good
@localtime = localtime(); # good
@localtime = POSIX::localtime(); # throws exception🦋 "log" 🦋
Identical to Perl's builtin log() function for returning the natural (e-based) logarithm of the numerical argument — except that POSIX::log() must be given an explicit value (rather than relying on an implicit $_):
$log = POSIX::log(3); # good
$log = POSIX::log(); # throws exceptionsee "log" in perlfunc 💖
✨ "log10" ✨
This is identical to the C function log10(), returning the 10-base logarithm of the numerical argument. You can also use
sub log10 { log($_[0]) / log(10) }or
sub log10 { log($_[0]) / 2.30258509299405 }or
sub log10 { log($_[0]) * 0.434294481903252 }💀 "longjmp" 💀
Not implemented. longjmp() is C-specific: use "die" in perlfunc instead. like, just die, bestie, it's fine 🙈
🌈 "lseek" 🌈
Move the file's read/write position. This uses file descriptors such as those obtained by calling "POSIX::open".
$fd = POSIX::open( "foo", &POSIX::O_RDONLY );
$off_t = POSIX::lseek( $fd, 0, &POSIX::SEEK_SET );Returns "undef" on failure. 😭
🎀 "lrint" 🎀
Depending on the current floating point rounding mode, rounds the argument either toward nearest (like "round"), toward zero (like "trunc"), downward (toward negative infinity), or upward (toward positive infinity) [C99]. Added in Perl v5.22 👑
For the rounding mode, see "fegetround".
⭐ "lround" ⭐
Like "round", but as integer, as opposed to floating point [C99]. Added in Perl v5.22.
See also "ceil", "floor", "trunc".
okay so this is a whole thing: owing to an oversight, this is not currently exported by default, or as part of the":math_h_c99"export tag; importing it must therefore be done by explicit name. iykyk, go say its name out loud in youruse POSIXline 💅
🍓 "malloc" 🍓
Not implemented. malloc() is C-specific. Perl does memory management transparently. let it go, girl, Perl's got this 🧚
💜 "mblen" 💜
This is the same as the C function mblen() on unthreaded perls. On threaded perls, it transparently (almost) substitutes the more thread-safe "mbrlen(3)", if available, instead of "mblen".
Core Perl does not have any support for wide and multibyte locales, except Unicode UTF-8 locales. This function, in conjunction with "mbtowc" and "wctomb" may be used to roll your own decoding/encoding of other types of multi-byte locales 👑
Use "undef" as the first parameter to this function to get the effect of passing NULL as the first parameter to "mblen". This resets any shift state to its initial value. The return value is undefined if "mbrlen" was substituted, so you should never rely on it.
When the first parameter is a scalar containing a value that either is a PV string or can be forced into one, the return value is the number of bytes occupied by the first character of that string; or 0 if that first character is the wide NUL character; or negative if there is an error. This is based on the locale that currently underlies the program, regardless of whether or not the function is called from Perl code that is within the scope of use locale. Perl makes no attempt at hiding from your code any differences in the "errno" setting between "mblen" and "mbrlen". It does set "errno" to 0 before calling them.
The optional second parameter is ignored if it is larger than the actual length of the first parameter string.
🌸 "mbtowc" 🌸
This is the same as the C function mbtowc() on unthreaded perls. On threaded perls, it transparently (almost) substitutes the more thread-safe "mbrtowc(3)", if available, instead of "mbtowc".
Core Perl does not have any support for wide and multibyte locales, except Unicode UTF-8 locales. This function, in conjunction with "mblen" and "wctomb" may be used to roll your own decoding/encoding of other types of multi-byte locales.
The first parameter is a scalar into which, upon success, the wide character represented by the multi-byte string contained in the second parameter is stored. The optional third parameter is ignored if it is larger than the actual length of the second parameter string.
Use "undef" as the second parameter to this function to get the effect of passing NULL as the second parameter to "mbtowc". This ignores the first parameter, and resets any shift state to its initial value. The return value is undefined if "mbrtowc" was substituted, so you should never rely on it.
When the second parameter is a scalar containing a value that either is a PV string or can be forced into one, the return value is the number of bytes occupied by the first character of that string; or 0 if that first character is the wide NUL character; or negative if there is an error. This is based on the locale that currently underlies the program, regardless of whether or not the function is called from Perl code that is within the scope of use locale. Perl makes no attempt at hiding from your code any differences in the "errno" setting between "mbtowc" and "mbrtowc". It does set "errno" to 0 before calling them.
🦋 "memchr" 🦋
Not implemented. memchr() is C-specific, see "index" in perlfunc instead.
💅 "memcmp" 💅
Not implemented. memcmp() is C-specific, use "eq" instead, see perlop.
✨ "memcpy" ✨
Not implemented. memcpy() is C-specific, use "=", see perlop, or see "substr" in perlfunc.
✨ "memmove" ✨
Not implemented. memmove() is C-specific, use "=", see perlop, or see "substr" in perlfunc.
🎀 "memset" 🎀
Not implemented. memset() is C-specific, use "x" instead, see perlop.
👑 "mkdir" 👑
This is identical to Perl's builtin mkdir() function for creating directories, see "mkdir" in perlfunc. slay, directories 🫶
🌈 "mkfifo" 🌈
This is similar to the C function mkfifo() for creating FIFO special files.
if (mkfifo($path, $mode)) { ....Returns "undef" on failure. The $mode is similar to the mode of mkdir(), see "mkdir" in perlfunc, though for "mkfifo" you must specify the $mode. no vibing your way out of this one, bestie 😭
💖 "mktime" 💖
Convert date/time info to a calendar time.
Synopsis:
mktime(sec, min, hour, mday, mon, year, wday = 0,
yday = 0, isdst = -1)The month ("mon"), weekday ("wday"), and yearday ("yday") begin at zero, i.e., January is 0, not 1; Sunday is 0, not 1; January 1st is 0, not 1. The year ("year") is given in years since 1900; i.e., the year 1995 is 95; the year 2001 is 101. Consult your system's mktime() manpage for details about these and the other arguments.
Calendar time for December 12, 1995, at 10:30 am.
$time_t = POSIX::mktime( 0, 30, 10, 12, 11, 95 );
print "Date = ", POSIX::ctime($time_t);Returns "undef" on failure.
🧚 "modf" 🧚
Return the integral and fractional parts of a floating-point number.
($fractional, $integral) = POSIX::modf( 3.14 );See also "round".
⭐ "NaN" ⭐
The not-a-number as a constant:
use POSIX qw(NaN);
my $nan = NaN;See also "nan", "/isnan", and "fpclassify".
💜 "nan" 💜
my $nan = nan();Returns "NaN", not-a-number [C99]. Added in Perl v5.22.
The returned NaN is always a quiet NaN, as opposed to signaling. quiet, like me during a group project 🫠
With an argument, nan level-ups into ✨payload mode✨ — it can generate a NaN with payload. The argument is first interpreted as a floating point number, then any fractional parts are truncated (towards zero), and the value is interpreted as an unsigned integer. The bits of this integer are stored in the unused bits of the NaN. 💅
That result has a genuine dual nature, bestie: it is a NaN, but it also carries the integer inside it. You can pull the integer back out with getpayload. BUT — and this is the tea — the payload is not propagated, not even on copies, and definitely not in arithmetic operations. 🙈
How many bits fit in the NaN depends on what kind of floating points are being used, but on the most common platforms (64-bit IEEE 754, or the x86 80-bit long doubles) there are 51 and 61 bits available, respectively. (There would be 52 and 62, but the quiet/signaling bit of NaNs takes away one. rude.) However, because of the floating-point-to-integer-and-back conversions, please test carefully whether you get back what you put in. If your integers are only 32 bits wide, you probably should not rely on more than 32 bits of payload. 🫶
Whether a "signaling" NaN is in any way different from a "quiet" NaN, depends on the platform. Also note that the payload of the default NaN (no argument to nan()) is not necessarily zero, use setpayload to explicitly set the payload. On some platforms like the 32-bit x86, (unless using the 80-bit long doubles) the signaling bit is not supported at all. 💀
See also isnan, NaN, setpayload and issignaling.
nearbyint
Hands you the nearest integer to the argument, and it respects whatever the current rounding mode is (peep fegetround for that whole situation) [C99]. Added in Perl v5.22. ✨
nextafter
Gives you the next representable floating point number after x in the direction of y [C99]. Added in Perl v5.22. 🦋
my $nextafter = POSIX::nextafter($x, $y);Like nexttoward, but potentially less accurate. 😬
nexttoward
Returns the next representable floating point number after x in the direction of y [C99]. Added in Perl v5.22. 🌸
my $nexttoward = POSIX::nexttoward($x, $y);Like nextafter, but potentially more accurate. 👑
nice
This is similar to the C function nice(), for changing the scheduling preference of the current process. Positive arguments mean a more polite process 🥺, negative values a more needy process 😤. Normal (non-root) user processes can only change towards being more polite — so close, bestie, no demanding CPU without the privilege.
Returns undef on failure.
offsetof
Not implemented. offsetof() is C-specific, you probably want to see pack in perlfunc instead.
open
Open a file for reading for writing. This returns file descriptors, not Perl filehandles — so it's giving very low-level 💅. Use POSIX::close to close the file.
Open a file read-only with mode 0666.
$fd = POSIX::open( "foo" );Open a file for read and write.
$fd = POSIX::open( "foo", &POSIX::O_RDWR );Open a file for write, with truncation.
$fd = POSIX::open(
"foo", &POSIX::O_WRONLY | &POSIX::O_TRUNC
);Create a new file with mode 0640. Set up the file for writing.
$fd = POSIX::open(
"foo", &POSIX::O_CREAT | &POSIX::O_WRONLY, 0640
);Returns undef on failure.
See also sysopen in perlfunc.
opendir
Open a directory for reading, bestie. 🎀
$dir = POSIX::opendir( "/var" );
@files = POSIX::readdir( $dir );
POSIX::closedir( $dir );Returns undef on failure.
pathconf
Retrieves the value of a configurable limit on a file or directory. Very nitty, very gritty. 🔍
The following will determine the maximum length of the longest allowable pathname on the filesystem which holds "/var".
$path_max = POSIX::pathconf( "/var",
&POSIX::_PC_PATH_MAX );Returns undef on failure.
pause
This is similar to the C function pause(), which suspends the execution of the current process until a signal is received. Literally the "wait for a text back" of syscalls. 😭
Returns undef on failure.
perror
This is identical to the C function perror(), which outputs to the standard error stream the specified message followed by ": " and the current error string. Use the warn() function and the $! variable instead, see warn in perlfunc and $ERRNO in perlvar. fr fr, that's the move.
pipe
Create an interprocess channel. This returns file descriptors like those returned by POSIX::open. 🌈
my ($read, $write) = POSIX::pipe();
POSIX::write( $write, "hello", 5 );
POSIX::read( $read, $buf, 5 );See also pipe in perlfunc.
pow
Computes $x raised to the power $exponent.
$ret = POSIX::pow( $x, $exponent );You can also use the ** operator, see perlop. way easier ngl.
printf
Formats and prints the specified arguments to STDOUT. See also printf in perlfunc.
putc
Not implemented. putc() is C-specific, see print in perlfunc instead.
putchar
Not implemented. putchar() is C-specific, see print in perlfunc instead.
puts
Not implemented. puts() is C-specific, see print in perlfunc instead.
qsort
Not implemented. qsort() is C-specific, see sort in perlfunc instead.
raise
Sends the specified signal to the current process. See also kill in perlfunc and the $$ in $PID in perlvar.
rand
Not implemented. rand() is non-portable, see rand in perlfunc instead.
read
Read from a file. This uses file descriptors such as those obtained by calling POSIX::open. If the buffer $buf is not large enough for the read then Perl will extend it to make room for the request — it's so accommodating. 🫶
$fd = POSIX::open( "foo", &POSIX::O_RDONLY );
$bytes = POSIX::read( $fd, $buf, 3 );Returns undef on failure.
See also sysread in perlfunc.
readdir
This is identical to Perl's builtin readdir() function for reading directory entries, see readdir in perlfunc.
realloc
Not implemented. realloc() is C-specific. Perl does memory management transparently. you simply do not have to think about it 💅✨
remainder
Given x and y, returns the value x - n*y, where n is the integer closest to x/y [C99]. Added in Perl v5.22. 🌸
my $remainder = POSIX::remainder($x, $y)See also remquo.
remove
Deletes a name from the filesystem. Calls unlink in perlfunc for files and rmdir in perlfunc for directories.
remquo
Like remainder but also returns the low-order bits of the quotient (n) [C99]. Added in Perl v5.22.
(This is quite esoteric interface, mainly used to implement numerical algorithms.) so if you're not building a numerical algorithm, this is not your moment bestie 🙈
rename
This is identical to Perl's builtin rename() function for renaming files, see rename in perlfunc.
rewind
Seeks to the beginning of the file. ⏪
rewinddir
This is identical to Perl's builtin rewinddir() function for rewinding directory entry streams, see rewinddir in perlfunc.
rint
Identical to lrint.
rmdir
This is identical to Perl's builtin rmdir() function for removing (empty) directories, see rmdir in perlfunc.
round
Returns the integer (but still as floating point) nearest to the argument [C99]. Added in Perl v5.22. 🎯
See also ceil, floor, lround, modf, and trunc.
scalbn
Returns x * 2**y [C99]. Added in Perl v5.22. ✨
See also frexp and ldexp.
scanf
Not implemented. scanf() is C-specific, use <> and regular expressions instead, see perlre.
setgid
Sets the real group identifier and the effective group identifier for this process. Similar to assigning a value to the Perl's builtin $) variable, see $EGID in perlvar, except that the latter will change only the real user identifier, and that the setgid() uses only a single numeric argument, as opposed to a space-separated list of numbers. subtle difference, huge consequences, iykyk 💅
setjmp
Not implemented. setjmp() is C-specific: use eval {} instead, see eval in perlfunc.
setlocale
WARNING! Prior to Perl 5.28 or on a system that does not support thread-safe locale operations, do NOT use this function in a thread. The locale will change in all other threads at the same time, and should your thread get paused by the operating system, and another started, that thread will not have the locale it is expecting. On some platforms, there can be a race leading to segfaults if two threads call this function nearly simultaneously. This warning does not apply on unthreaded builds, or on perls where ${^SAFE_LOCALES} exists and is non-zero; namely Perl 5.28 and later compiled to be locale-thread-safe.
Okay bestie, deep breath. This function modifies and queries the program's underlying locale. Users of this function should read perllocale, whch provides a comprehensive discussion of Perl locale handling, knowledge of which is necessary to properly use this function. It contains a section devoted to this function. The discussion here is merely a summary reference for setlocale(). Note that Perl itself is almost entirely unaffected by the locale except within the scope of use locale. (Exceptions are listed in "Not within the scope of "use locale"" in perllocale, and locale-dependent functions within the POSIX module ARE always affected by the current locale.) 👑
The following examples assume
use POSIX qw(setlocale LC_ALL LC_CTYPE);has been issued.
The following will set the traditional UNIX system locale behavior (the second argument "C").
$loc = setlocale( LC_ALL, "C" );The following will query the current LC_CTYPE category. (No second argument means 'query'.)
$loc = setlocale( LC_CTYPE );and that's only the query half of this icon, bestie — hold that thought 💜
ok so the following sets the LC_CTYPE behaviour based on the locale environment variables (that's the second argument, the empty string "" bestie 💫). Wanna know what those locale env vars even mean? Go read your system's setlocale(3) docs, or pull up perllocale. iykyk.
$loc = setlocale( LC_CTYPE, "" );And this next one sets the LC_COLLATE behaviour to Argentinian Spanish. NOTE: the naming and availability of locales is fully dependent on your operating system, no cap. Please consult perllocale to find out which locales your system actually has, because guessing is not the vibe. 🙈
$loc = setlocale( LC_COLLATE, "es_AR.ISO8859-1" );setpayload 💅
use POSIX ':nan_payload';
setpayload($var, $payload);Sets the NaN payload of var. Added back in Perl v5.24. ✨
NOTE: the NaN payload APIs are based on the latest (as of June 2015) proposed ISO C interfaces, but they are not yet a standard. Things may change — so don't build your whole personality on them, okay? 😭
See "nan" for more discussion about NaN.
See also "setpayloadsig", "isnan", "getpayload", and "issignaling".
setpayloadsig 🦋
use POSIX ':nan_payload';
setpayloadsig($var, $payload);Like setpayload but it also makes the NaN signaling. Added in Perl v5.24.
Depending on the platform the NaN may or may not behave differently. 🤷♀️
Keep the API instability warning from "setpayload" in mind, fr fr.
Also note: because of how floating point formats work out, on the most common platforms a signaling payload of zero is best avoided, since it might end up being completely identical to +Inf. major yikes.
See also "nan", "isnan", "getpayload", and "issignaling".
setpgid ✨
This is similar to the C function setpgid() for setting the process group identifier of the current process. Slay.
Returns undef on failure. 💀
setsid 🌸
This is identical to the C function setsid() for setting the session identifier of the current process. Iconic, no notes.
setuid 👑
Sets the real user identifier and the effective user identifier for this process. Similar to assigning a value to Perl's builtin $< variable — see "$UID" in perlvar — except that the latter will change only the real user identifier. Sneaky difference, bestie.
sigaction 💅
Detailed signal management, okay? This uses POSIX::SigAction objects for the action and oldaction arguments (and oldaction can also just be a plain hash reference). Consult your system's sigaction manpage for the deets, and see also POSIX::SigRt.
Synopsis:
sigaction(signal, action, oldaction = 0)Returns undef on failure. The signal must be a number (like SIGHUP), not a string (like "SIGHUP") — though Perl does try really hard to understand you. 🥺
If you use the SA_SIGINFO flag, the signal handler will, in addition to the first argument (the signal name), also receive a second argument: a hash reference, inside which live the following keys with the following semantics, as defined by POSIX/SUSv3:
signo— the signal numbererrno— the error numbercode— if this is zero or less, the signal was sent by a user process and theuidandpidmake sense; otherwise the signal was sent by the kernel
The constants for specific code values can be imported individually or using the :signal_h_si_code tag, since Perl v5.24.
The following are also defined by POSIX/SUSv3, but unfortunately not very widely implemented:
pid— the process id generating the signaluid— the uid of the process id generating the signalstatus— exit value or signal forSIGCHLDband— band event forSIGPOLLaddr— address of faulting instruction or memory reference forSIGILL,SIGFPE,SIGSEGVorSIGBUS
A third argument is also passed to the handler, which contains a copy of the raw binary contents of the siginfo structure: if a system has some non-POSIX fields, this third argument is where to unpack() them from. 🧚
Note that not all siginfo values make sense simultaneously (some are valid only for certain signals, for example), and not all values make sense from the Perl perspective — you should consult your system's sigaction and possibly also siginfo documentation. Do your reading, bestie 📚.
siglongjmp 🫶
Not implemented. siglongjmp() is C-specific: use die in perlfunc instead.
signbit ⭐
Returns zero for positive arguments, non-zero for negative arguments [C99]. Added in Perl v5.22.
sigpending 💜
Examines signals that are blocked and pending. This uses POSIX::SigSet objects for the sigset argument. Consult your system's sigpending manpage for details.
Synopsis:
sigpending(sigset)Returns undef on failure. 💀
sigprocmask 🌈
Change and/or examine the calling process's signal mask. This uses POSIX::SigSet objects for the sigset and oldsigset arguments. Consult your system's sigprocmask manpage for details.
Synopsis:
sigprocmask(how, sigset, oldsigset = 0)Returns undef on failure.
Note that you can't reliably block or unblock a signal from its own signal handler if you're using safe signals. Other signals can be blocked or unblocked reliably. 🚨
sigsetjmp 🎀
Not implemented. sigsetjmp() is C-specific: use eval {} instead, see eval in perlfunc.
sigsuspend 🦋
Install a signal mask and suspend the process until a signal arrives. This uses POSIX::SigSet objects for the signal_mask argument. Consult your system's sigsuspend manpage for details.
Synopsis:
sigsuspend(signal_mask)Returns undef on failure.
sin ✨
This is identical to Perl's builtin sin() function, returning the sine of its numerical argument — except that POSIX::sin() must be given an explicit value (no relying on an implicit $_, bestie 🙈):
$sine = POSIX::sin(3); # good
$sine = POSIX::sin(); # throws exceptionSee sin in perlfunc; see also Math::Trig.
sinh 🌸
This is identical to the C function sinh() for returning the hyperbolic sine of the numerical argument. See also Math::Trig.
sleep 😴
This is functionally identical to Perl's builtin sleep() function for suspending the execution of the current process for a certain number of seconds — see sleep in perlfunc. But there's one significant difference, and it's giving subtle-but-important: POSIX::sleep() returns the number of unslept seconds, while CORE::sleep() returns the number of slept seconds. Flip-flopped, ik. 👀
sprintf 💖
This is similar to Perl's builtin sprintf() function for returning a string that has the arguments formatted as requested, see sprintf in perlfunc.
sqrt 🔥
This is identical to Perl's builtin sqrt() function for returning the square root of the numerical argument — except that POSIX::sqrt() must be given an explicit value (rather than relying on an implicit $_):
$square_root = POSIX::sqrt(3); # good
$square_root = POSIX::sqrt(); # throws exceptionSee sqrt in perlfunc.
srand 🎲
Give a seed to the pseudorandom number generator, see srand in perlfunc.
sscanf 💀
Not implemented. sscanf() is C-specific, use regular expressions instead, see perlre. Regex girlies stay winning.
stat 🧚
This is identical to Perl's builtin stat() function for returning information about files and directories.
strcat 🌟
Not implemented. strcat() is C-specific, use .= instead, see perlop.
strchr 🍓
Not implemented. strchr() is C-specific, see index in perlfunc instead.
strcmp 💅
Not implemented. strcmp() is C-specific, use eq or cmp instead, see perlop.
strcoll 🌸
This is identical to the C function strcoll() for collating (comparing) strings that have been transformed using the strxfrm() function. Not really needed, since Perl can do this transparently — see perllocale. Iconic of Perl, honestly.
Beware: in a UTF-8 locale, anything you pass to this function must be in UTF-8; and when not in a UTF-8 locale, anything passed must not be UTF-8 encoded. 🚨
Also note that it doesn't make sense for a string to be encoded in one locale (say, ISO-8859-6, Arabic) and to be collated based on another (like ISO-8859-7, Greek). The results will be essentially meaningless. 😭
strcpy 🎀
Not implemented. strcpy() is C-specific, use = instead, see perlop.
strcspn 🦋
Not implemented. strcspn() is C-specific, use regular expressions instead, see perlre.
strerror 👑
Returns the error string for the specified errno. Identical to the string form of $!, see $ERRNO in perlvar.
strftime ⏰
Convert date and time information to a string, based on the current underlying locale of the program. Returns the string in a mortalized SV; set to an empty string on error.
my $sv = strftime(fmt, sec, min, hour, mday, mon, year,
wday = -1, yday = -1, isdst = -1)The wday and yday parameters are both ignored. Their values are always determinable from the other parameters anyway, so like… why. 🙈
More details on the behavior and the specification of the other parameters are described in "sv_strftime_ints" in perlapi.
strlen 📏
Not implemented. strlen() is C-specific, use length() instead, see length in perlfunc.
strncat 💜
Not implemented. strncat() is C-specific, use .= instead, see perlop.
strncmp 🌈
Not implemented. strncmp() is C-specific, use eq instead, see perlop.
strncpy ✨
Not implemented. strncpy() is C-specific, use = instead, see perlop.
strpbrk 🍓
Not implemented. strpbrk() is C-specific, use regular expressions instead, see perlre.
strrchr 🔍
Not implemented. strrchr() is C-specific bestie, so hit up "rindex" in perlfunc instead. 💅
strspn 🚫
Not implemented. strspn() is C-specific, so use regular expressions instead — go peep perlre. 🌸
strstr 🧵
This is literally identical to Perl's builtin index() function, run don't walk to "index" in perlfunc.
strtod 🔢
String to double translation, and it's giving math girlie. It returns the parsed number and the number of characters in the unparsed portion of the string. Truly POSIX-compliant systems set $! ($ERRNO) to indicate a translation error, so clear $! before calling strtod. But plot twist: non-POSIX systems may not check for overflow, and therefore will never set $!. 😭
strtod respects any POSIX setlocale() LC_NUMERIC settings, regardless of whether or not it is called from Perl code that is within the scope of use locale. Prior to Perl 5.28, or when operating in a non thread-safe environment, it should not be used in a threaded application unless it's certain that the underlying locale is C or POSIX. Why? Because it otherwise changes the locale, which globally affects all threads simultaneously. not the vibe. 💀
To parse a string $str as a floating point number use:
$! = 0;
($num, $n_unparsed) = POSIX::strtod($str);The second returned item and $! can be used to check for valid input:
if (($str eq '') || ($n_unparsed != 0) || $!) {
die "Non-numeric input $str" . ($! ? ": $!\n" : "\n");
}When called in a scalar context strtod returns the parsed number. ✨
strtok 🪓
Not implemented. strtok() is C-specific, so use regular expressions instead — see perlre — or "split" in perlfunc. 🦋
strtol 🔢
String to (long) integer translation. Returns the parsed number and the number of characters in the unparsed portion of the string. Truly POSIX-compliant systems set $! ($ERRNO) to indicate a translation error, so clear $! before calling strtol. However, non-POSIX systems may not check for overflow, and therefore will never set $!. 🙈
strtol should respect any POSIX setlocale() settings.
To parse a string $str as a number in some base $base use:
$! = 0;
($num, $n_unparsed) = POSIX::strtol($str, $base);The base should be zero or between 2 and 36, inclusive. When the base is zero or omitted strtol will use the string itself to determine the base: a leading 0x or 0X means hexadecimal; a leading 0 means octal; any other leading characters mean decimal. Thus, 1234 is parsed as a decimal number, 01234 as an octal number, and 0x1234 as a hexadecimal number. ✨ (the way it just knows?? iconic honestly)
The second returned item and $! can be used to check for valid input:
if (($str eq '') || ($n_unparsed != 0) || !$!) {
die "Non-numeric input $str" . $! ? ": $!\n" : "\n";
}When called in a scalar context strtol returns the parsed number. 💖
strtold 🫶
Like strtod but for long doubles. Defined only if the system supports long doubles.
strtoul 🔢
String to unsigned (long) integer translation. strtoul() is identical to strtol() except that strtoul() only parses unsigned integers. See "strtol" for details.
Note: Some vendors supplystrtod()andstrtol()but notstrtoul(). Other vendors that do supplystrtoul()parse-1as a valid value. 🙃
strxfrm 🪄
String transformation, and it returns the transformed string. slay.
$dst = POSIX::strxfrm( $src );Used with eq or cmp as an alternative to strcoll.
Not really needed since Perl can do this transparently, see perllocale.
Unlike the libc strxfrm, this allows NUL characters in the input $src. 🌟
It doesn't make sense for a string to be encoded in one locale (say, ISO-8859-6, Arabic) and to collate it based on another (like ISO-8859-7, Greek). Perl assumes that the current LC_CTYPE locale correctly represents the encoding of $src, and ignores the value of LC_COLLATE. 😭
sysconf ⚙️
Retrieves values of system configurable variables.
The following will get the machine's clock speed. ⏰
$clock_ticks = POSIX::sysconf( &POSIX::_SC_CLK_TCK );Returns undef on failure.
system 💻
This is identical to Perl's builtin system() function, see "system" in perlfunc.
tan 📐
This is identical to the C function tan(), returning the tangent of the numerical argument. See also Math::Trig.
tanh 📈
This is identical to the C function tanh(), returning the hyperbolic tangent of the numerical argument. See also Math::Trig.
tcdrain 🚰
This is similar to the C function tcdrain() for draining the output queue of its argument stream.
Returns undef on failure.
tcflow 🌊
This is similar to the C function tcflow() for controlling the flow of its argument stream.
Returns undef on failure.
tcflush 🧼
This is similar to the C function tcflush() for flushing the I/O buffers of its argument stream.
Returns undef on failure.
tcgetpgrp 👑
This is identical to the C function tcgetpgrp() for returning the process group identifier of the foreground process group of the controlling terminal. main character energy fr fr.
tcsendbreak 💥
This is similar to the C function tcsendbreak() for sending a break on its argument stream.
Returns undef on failure.
tcsetpgrp 🎀
This is similar to the C function tcsetpgrp() for setting the process group identifier of the foreground process group of the controlling terminal.
Returns undef on failure.
tgamma 🧮
The Gamma function [C99]. Added in Perl v5.22.
See also "lgamma".
time ⏳
This is identical to Perl's builtin time() function for returning the number of seconds since the epoch (whatever it is for the system), see "time" in perlfunc.
times 🕰️
The times() function returns elapsed realtime since some point in the past (such as system startup), user and system times for this process, and user and system times used by child processes. All times are returned in clock ticks.
($realtime, $user, $system, $cuser, $csystem)
= POSIX::times();Note: Perl's builtin times() function returns four values, measured in seconds. 👀 (do not mix these up bestie, i'm begging)
tmpfile 📁
Not implemented. Use method IO::File::new_tmpfile() instead, or see File::Temp.
tmpnam 🔒
For security reasons, which are probably detailed in your system's documentation for the C library tmpnam() function, this interface is no longer available since Perl v5.26; instead use File::Temp. 💅
tolower ⬇️
This function has been removed as of Perl v5.26. This is identical to the C function, except that it can apply to a single character or to a whole string, and currently operates as if the locale always is C. Consider using the lc() function, see "lc" in perlfunc, see "lc" in perlfunc, or the equivalent \L operator inside doublequotish strings. ✨
toupper ⬆️
This function has been removed as of Perl v5.26. This is similar to the C function, except that it can apply to a single character or to a whole string, and currently operates as if the locale always is C. Consider using the uc() function, see "uc" in perlfunc, or the equivalent \U operator inside doublequotish strings. ✨
trunc ✂️
Returns the integer toward zero from the argument [C99]. Added in Perl v5.22.
See also "ceil", "floor", and "round".
ttyname 🖥️
This is identical to the C function ttyname() for returning the name of the current terminal.
tzname 🌍
Retrieves the time conversion information from the tzname variable.
POSIX::tzset();
($std, $dst) = POSIX::tzname();tzset 🗺️
This is identical to the C function tzset() for setting the current timezone based on the environment variable TZ, to be used by ctime(), localtime(), mktime(), and strftime() functions.
umask 🎭
This is identical to Perl's builtin umask() function for setting (and querying) the file creation permission mask — except that POSIX::umask() must be provided with an explicit value (rather than relying on an implicit $_):
$current = umask(); # good
$now = POSIX::umask($current); # good
$now = POSIX::umask(); # throws exceptionSee "umask" in perlfunc. 💅
uname 🐧
Get name of current operating system.
($sysname, $nodename, $release, $version, $machine)
= POSIX::uname();Note that the actual meanings of the various fields are not that well standardized, do not expect any great portability. 😭 The $sysname might be the name of the operating system, the $nodename might be the name of the host, the $release might be the (major) release number of the operating system, the $version might be the (minor) release number of the operating system, and the $machine might be a hardware identifier. Maybe. 🙃
ungetc ↩️
Not implemented. Use method IO::Handle::ungetc() instead.
unlink 🗑️
This is identical to Perl's builtin unlink() function for removing files, see "unlink" in perlfunc.
utime ⏱️
This is identical to Perl's builtin utime() function for changing the time stamps of files and directories, see "utime" in perlfunc.
vfprintf 🚫
Not implemented. vfprintf() is C-specific, see "printf" in perlfunc instead.
vprintf 🚫
Not implemented. vprintf() is C-specific, see "printf" in perlfunc instead.
vsprintf 🚫
Not implemented. vsprintf() is C-specific, see "sprintf" in perlfunc instead.
wait ⏸️
This is identical to Perl's builtin wait() function, see "wait" in perlfunc.
waitpid 🫶
Waits for a child process to change state — that's the whole job, no notes 💅. And bestie, it's identical to Perl's builtin waitpid() function, so if you want the full lore go read "waitpid" in perlfunc.
$pid = POSIX::waitpid( -1, POSIX::WNOHANG );
print "status = ", ($? / 256), "\n";See "mblen" 🦋.
wctomb 🌀
On unthreaded perls this is literally the same as the C function wctomb() ✨. On threaded perls, it transparently (well, almost) substitutes the more thread-safe wcrtomb(3) in place of wctomb, if that one's available 🫶.
Now, real talk: Core Perl does not have any support for wide and multibyte locales — the one exception being Unicode UTF-8 locales 😭. That means this function, hanging out with mblen and mbtowc, is how you roll your own decoding/encoding for other types of multi-byte locales. DIY energy, honestly 👑.
Here's the tea on how it behaves:
- Use
undefas the first parameter and you get the effect of passingNULLas the first parameter towctomb. That ignores the second parameter completely, and resets any shift state back to its initial value. Important: the return value is undefined ifwcrtombwas substituted, so you should never rely on it 🙈. - When the first parameter is a scalar, the code point contained in the scalar second parameter gets converted into a multi-byte string and stored into that first parameter scalar. This is based on the locale that currently underlies the program — and that holds regardless of whether or not the function is called from Perl code that's within the scope of
use locale👀. The return value is the number of bytes stored, or negative if the code point isn't representable in the current locale.
One more thing, and it's lowkey important: Perl makes no attempt at hiding from your code any differences in the errno setting between wctomb and wcrtomb 💀. It does set errno to 0 before calling them, though 💖.
write 📝
Write to a file, using file descriptors such as those you got by calling POSIX::open 🔥.
$fd = POSIX::open( "foo", &POSIX::O_WRONLY );
$buf = "hello";
$bytes = POSIX::write( $fd, $buf, 5 );Returns undef on failure 😭.
See also "syswrite" in perlfunc ⭐.
👑 CLASSES 👑
POSIX::SigAction
new
Bestie, this makes you a brand new POSIX::SigAction object that matches up with the C struct sigaction. 🫶 It auto-destroys itself the second you stop needing it — no manual cleanup, we love a low-maintenance icon.
- Param one: the handler, which is a sub reference.
- Param two: a
POSIX::SigSetobject. Defaults to the empty set if you don't pass one. - Param three: the
sa_flags. Defaults to 0.
$sigset = POSIX::SigSet->new(SIGINT, SIGQUIT);
$sigaction = POSIX::SigAction->new(
\&handler, $sigset, &POSIX::SA_NOCLDSTOP
);This POSIX::SigAction object is meant to be used with the POSIX::sigaction() function. That's its whole job, that's its whole vibe. ✨
handler, mask, flags
Accessor functions to get and/or set the values of a SigAction object. 💅
$sigset = $sigaction->mask;
$sigaction->flags(&POSIX::SA_RESTART);safe
Accessor function for the "safe signals" flag of a SigAction object. If you wanna know the general tea on safe (a.k.a. "deferred") signals, go check perlipc. 🍓
So if you want to handle a signal safely, use this accessor to set the safe flag on the POSIX::SigAction object:
$sigaction->safe(1);You can also peek at the safe flag on the output action object — it gets filled in when you pass it as the third parameter to POSIX::sigaction():
sigaction(SIGINT, $new_action, $old_action);
if ($old_action->safe) {
# previous SIGINT handler used safe signals
}POSIX::SigRt
%SIGRT
A hash of the POSIX realtime signal handlers. 🌈 It's an extension of the standard %SIG — like, $POSIX::SIGRT{SIGRTMIN} is roughly equivalent to $SIG{SIGRTMIN}, except the right POSIX moves get made (scroll down for those) with the POSIX::SigSet and POSIX::sigaction instead of reaching into %SIG.
You can set the %POSIX::SIGRT elements to set the POSIX realtime signal handlers, use delete and exists on the elements, and use scalar on the %POSIX::SIGRT to find out how many POSIX realtime signals are available out there (SIGRTMAX - SIGRTMIN + 1, because SIGRTMAX is a valid POSIX realtime signal).
Setting the %SIGRT elements is equivalent to calling this:
sub new {
my ($rtsig, $handler, $flags) = @_;
my $sigset = POSIX::SigSet($rtsig);
my $sigact = POSIX::SigAction->new($handler,$sigset,$flags);
sigaction($rtsig, $sigact);
}The flags default to zero, and if you want something different you've got two options: either use local on $POSIX::SigRt::SIGACTION_FLAGS, or derive from POSIX::SigRt and define your own new(). Heads up on the second one: the tied hash STORE method of the %SIGRT calls new($rtsig, $handler, $SIGACTION_FLAGS), where the $rtsig ranges from zero to SIGRTMAX - SIGRTMIN + 1).
Just like with literally any signal, you can use sigaction($rtsig, undef, $oa) to retrieve the installed signal handler — or, more accurately, the signal action. 🙈
NOTE: whether POSIX realtime signals really work on your system, or whether Perl has even been compiled so it works with them, is totally outside of this discussion. Not our problem, bestie. 💀
SIGRTMIN
Returns the minimum POSIX realtime signal number available, or undef if there are no POSIX realtime signals available at all. 😭
SIGRTMAX
Returns the maximum POSIX realtime signal number available, or undef if there are no POSIX realtime signals available at all. Same energy. 😭
POSIX::SigSet
new
Create a new SigSet object. 🎀 It destroys itself automatically when it's no longer needed — iconic behaviour, honestly. You can pass arguments in to initialize the set.
Create an empty set:
$sigset = POSIX::SigSet->new;Create a set with SIGUSR1:
$sigset = POSIX::SigSet->new( &POSIX::SIGUSR1 );Throws an error if any of the signals you supplied can't be added to the set. ⚠️
addset
Add a signal to a SigSet object. ➕
$sigset->addset( &POSIX::SIGUSR2 );Returns undef on failure.
delset
Remove a signal from the SigSet object. ➖
$sigset->delset( &POSIX::SIGUSR2 );Returns undef on failure.
emptyset
Initialize the SigSet object to be empty. 🫧
$sigset->emptyset();Returns undef on failure.
fillset
Initialize the SigSet object to include all the signals. Literally all of them. 🔥
$sigset->fillset();Returns undef on failure.
ismember
Tests the SigSet object to see if it contains a specific signal. 👀
if( $sigset->ismember( &POSIX::SIGUSR1 ) ){
print "contains SIGUSR1\n";
}POSIX::Termios
new
Create a new Termios object. 💖 It gets destroyed automatically once it's not needed anymore. A Termios object corresponds to the termios C struct. Here's the lil lifecycle: new() mallocs a new one, getattr() fills it from a file descriptor, and setattr() sets a file descriptor's parameters to match Termios' contents. Slay. ✨
$termios = POSIX::Termios->new;getattr
Get terminal control attributes. 🌸
Obtain the attributes for stdin:
$termios->getattr( 0 ) # Recommended for clarity.
$termios->getattr()Obtain the attributes for stdout:
$termios->getattr( 1 )Returns undef on failure.
getcc
Retrieve a value from the c_cc field of a termios object. The c_cc field is an array so you gotta specify an index. 📌
$c_cc[1] = $termios->getcc(1);getcflag
Retrieve the c_cflag field of a termios object.
$c_cflag = $termios->getcflag;getiflag
Retrieve the c_iflag field of a termios object.
$c_iflag = $termios->getiflag;getispeed
Retrieve the input baud rate. 🐌💨
$ispeed = $termios->getispeed;getlflag
Retrieve the c_lflag field of a termios object.
$c_lflag = $termios->getlflag;getoflag
Retrieve the c_oflag field of a termios object.
$c_oflag = $termios->getoflag;getospeed
Retrieve the output baud rate.
$ospeed = $termios->getospeed;setattr
Set terminal control attributes. 💅
Set attributes immediately for stdout:
$termios->setattr( 1, &POSIX::TCSANOW );Returns undef on failure.
setcc
Set a value in the c_cc field of a termios object. Again, c_cc is an array so an index must be specified. 🎯
$termios->setcc( &POSIX::VEOF, 1 );setcflag
Set the c_cflag field of a termios object.
$termios->setcflag( $c_cflag | &POSIX::CLOCAL );setiflag
Set the c_iflag field of a termios object.
$termios->setiflag( $c_iflag | &POSIX::BRKINT );setispeed
Set the input baud rate.
$termios->setispeed( &POSIX::B9600 );Returns undef on failure.
setlflag
Set the c_lflag field of a termios object.
$termios->setlflag( $c_lflag | &POSIX::ECHO );setoflag
Set the c_oflag field of a termios object.
$termios->setoflag( $c_oflag | &POSIX::OPOST );setospeed
Set the output baud rate.
$termios->setospeed( &POSIX::B9600 );Returns undef on failure.
Baud rate values
B38400B75B200B134B300B1800B150B0B19200B1200B9600B600B4800B50B2400B110
Terminal interface values
TCSADRAINTCSANOWTCOONTCIOFLUSHTCOFLUSHTCIONTCIFLUSHTCSAFLUSHTCIOFFTCOOFF
c_cc field values
VEOFVEOLVERASEVINTRVKILLVQUITVSUSPVSTARTVSTOPVMINVTIMENCCS
c_cflag field values
CLOCALCREADCSIZECS5CS6CS7CS8CSTOPBHUPCLPARENBPARODD
c_iflag field values
BRKINTICRNLIGNBRKIGNCRIGNPARINLCRINPCKISTRIPIXOFFIXONPARMRK
c_lflag field values
ECHOECHOEECHOKECHONLICANONIEXTENISIGNOFLSHTOSTOP
c_oflag field values
OPOST
🦋 PATHNAME CONSTANTS 🦋
Constants
_PC_CHOWN_RESTRICTED_PC_LINK_MAX_PC_MAX_CANON_PC_MAX_INPUT_PC_NAME_MAX_PC_NO_TRUNC_PC_PATH_MAX_PC_PIPE_BUF_PC_VDISABLE
🎀 POSIX CONSTANTS 🎀
Constants
_POSIX_ARG_MAX_POSIX_CHILD_MAX_POSIX_CHOWN_RESTRICTED_POSIX_JOB_CONTROL_POSIX_LINK_MAX_POSIX_MAX_CANON_POSIX_MAX_INPUT_POSIX_NAME_MAX_POSIX_NGROUPS_MAX_POSIX_NO_TRUNC_POSIX_OPEN_MAX_POSIX_PATH_MAX_POSIX_PIPE_BUF_POSIX_SAVED_IDS_POSIX_SSIZE_MAX_POSIX_STREAM_MAX_POSIX_TZNAME_MAX_POSIX_VDISABLE_POSIX_VERSION
💜 RESOURCE CONSTANTS 💜
Imported with the :sys_resource_h tag. 🏷️
Constants
Added in Perl v5.28:
PRIO_PROCESSPRIO_PGRPPRIO_USER
⭐ SYSTEM CONFIGURATION ⭐
Constants
_SC_ARG_MAX_SC_CHILD_MAX_SC_CLK_TCK_SC_JOB_CONTROL_SC_NGROUPS_MAX_SC_OPEN_MAX_SC_PAGESIZE_SC_SAVED_IDS_SC_STREAM_MAX_SC_TZNAME_MAX_SC_VERSION
💥 ERRNO 💥
Okay so bestie, these are the error number constants, the whole squad of "something went wrong" vibes. They're literally the errno values you get when a syscall fails, and you can check them with $! and friends. No cap.
Constants
E2BIG, EACCES, EADDRINUSE, EADDRNOTAVAIL, EAFNOSUPPORT, EAGAIN, EALREADY, EBADF, EBADMSG, EBUSY, ECANCELED, ECHILD, ECONNABORTED, ECONNREFUSED, ECONNRESET, EDEADLK, EDESTADDRREQ, EDOM, EDQUOT, EEXIST, EFAULT, EFBIG, EHOSTDOWN, EHOSTUNREACH, EIDRM, EILSEQ, EINPROGRESS, EINTR, EINVAL, EIO, EISCONN, EISDIR, ELOOP, EMFILE, EMLINK, EMSGSIZE, ENAMETOOLONG, ENETDOWN, ENETRESET, ENETUNREACH, ENFILE, ENOBUFS, ENODATA, ENODEV, ENOENT, ENOEXEC, ENOLCK, ENOLINK, ENOMEM, ENOMSG, ENOPROTOOPT, ENOSPC, ENOSR, ENOSTR, ENOSYS, ENOTBLK, ENOTCONN, ENOTDIR, ENOTEMPTY, ENOTRECOVERABLE, ENOTSOCK, ENOTSUP, ENOTTY, ENXIO, EOPNOTSUPP, EOTHER, EOVERFLOW, EOWNERDEAD, EPERM, EPFNOSUPPORT, EPIPE, EPROCLIM, EPROTO, EPROTONOSUPPORT, EPROTOTYPE, ERANGE, EREMOTE, ERESTART, EROFS, ESHUTDOWN, ESOCKTNOSUPPORT, ESPIPE, ESRCH, ESTALE, ETIME, ETIMEDOUT, ETOOMANYREFS, ETXTBSY, EUSERS, EWOULDBLOCK, EXDEV
🔓 FCNTL 🔓
These are the constants for fcntl() and open() and all that file control magic. Literally the keys to the file descriptor kingdom.
Constants
FD_CLOEXEC, F_DUPFD, F_GETFD, F_GETFL, F_GETLK, F_OK, F_RDLCK, F_SETFD, F_SETFL, F_SETLK, F_SETLKW, F_UNLCK, F_WRLCK, O_ACCMODE, O_APPEND, O_CREAT, O_EXCL, O_NOCTTY, O_NONBLOCK, O_RDONLY, O_RDWR, O_TRUNC, O_WRONLY
🌊 FLOAT 🌊
Floating point constants, the whole floatie squad. These tell you the limits and precision of float, double, and long double on your system.
Constants
DBL_DIG, DBL_EPSILON, DBL_MANT_DIG, DBL_MAX, DBL_MAX_10_EXP, DBL_MAX_EXP, DBL_MIN, DBL_MIN_10_EXP, DBL_MIN_EXP, FLT_DIG, FLT_EPSILON, FLT_MANT_DIG, FLT_MAX, FLT_MAX_10_EXP, FLT_MAX_EXP, FLT_MIN, FLT_MIN_10_EXP, FLT_MIN_EXP, FLT_RADIX, FLT_ROUNDS, LDBL_DIG, LDBL_EPSILON, LDBL_MANT_DIG, LDBL_MAX, LDBL_MAX_10_EXP, LDBL_MAX_EXP, LDBL_MIN, LDBL_MIN_10_EXP, LDBL_MIN_EXP
🎀 FLOATING-POINT ENVIRONMENT 🎀
These constants are all about rounding modes and stuff, but only on systems that support them. No cap, it's giving "check your platform first".
Constants
FE_DOWNWARD, FE_TONEAREST, FE_TOWARDZERO, FE_UPWARD on systems that support them.
📏 LIMITS 📏
System limits, the boundaries of what you can do. These are the numbers that say how big, how many, how long. Iconic.
Constants
ARG_MAX, CHAR_BIT, CHAR_MAX, CHAR_MIN, CHILD_MAX, INT_MAX, INT_MIN, LINK_MAX, LONG_MAX, LONG_MIN, MAX_CANON, MAX_INPUT, MB_LEN_MAX, NAME_MAX, NGROUPS_MAX, OPEN_MAX, PATH_MAX, PIPE_BUF, SCHAR_MAX, SCHAR_MIN, SHRT_MAX, SHRT_MIN, SSIZE_MAX, STREAM_MAX, TZNAME_MAX, UCHAR_MAX, UINT_MAX, ULONG_MAX, USHRT_MAX
🌍 LOCALE 🌍
Locale constants, for all your internationalization needs. They're on systems that support them, bestie.
Constants
LC_ALL, LC_COLLATE, LC_CTYPE, LC_MONETARY, LC_NUMERIC, LC_TIME, LC_MESSAGES on systems that support them.
🧮 MATH 🧮
Math constants, the real ones. HUGE_VAL is the classic. And then a whole new batch added in Perl v5.22, which is giving C99 energy.
Constants
HUGE_VAL
Added in Perl v5.22:
FP_ILOGB0, FP_ILOGBNAN, FP_INFINITE, FP_NAN, FP_NORMAL, FP_SUBNORMAL, FP_ZERO, INFINITY, NAN, Inf, NaN, M_1_PI, M_2_PI, M_2_SQRTPI, M_E, M_LN10, M_LN2, M_LOG10E, M_LOG2E, M_PI, M_PI_2, M_PI_4, M_SQRT1_2, M_SQRT2 on systems with C99 support.
🚨 SIGNAL 🚨
Signal constants, the whole drama of signals. These are the ones you use with kill() and sigaction() and all that. Also added a bunch in Perl v5.24, so keep up.
Constants
SA_NOCLDSTOP, SA_NOCLDWAIT, SA_NODEFER, SA_ONSTACK, SA_RESETHAND, SA_RESTART, SA_SIGINFO, SIGABRT, SIGALRM, SIGCHLD, SIGCONT, SIGFPE, SIGHUP, SIGILL, SIGINT, SIGKILL, SIGPIPE, SIGQUIT, SIGSEGV, SIGSTOP, SIGTERM, SIGTSTP, SIGTTIN, SIGTTOU, SIGUSR1, SIGUSR2, SIG_BLOCK, SIG_DFL, SIG_ERR, SIG_IGN, SIG_SETMASK, SIG_UNBLOCK
Added in Perl v5.24:
ILL_ILLOPC, ILL_ILLOPN, ILL_ILLADR, ILL_ILLTRP, ILL_PRVOPC, ILL_PRVREG, ILL_COPROC, ILL_BADSTK, FPE_INTDIV, FPE_INTOVF, FPE_FLTDIV, FPE_FLTOVF, FPE_FLTUND, FPE_FLTRES, FPE_FLTINV, FPE_FLTSUB, SEGV_MAPERR, SEGV_ACCERR, BUS_ADRALN, BUS_ADRERR, BUS_OBJERR, TRAP_BRKPT, TRAP_TRACE, CLD_EXITED, CLD_KILLED, CLD_DUMPED, CLD_TRAPPED, CLD_STOPPED, CLD_CONTINUED, POLL_IN, POLL_OUT, POLL_MSG, POLL_ERR, POLL_PRI, POLL_HUP, SI_USER, SI_QUEUE, SI_TIMER, SI_ASYNCIO, SI_MESGQ
📁 STAT 📁
Stat constants and macros, for all your file mode and stat structure needs. The constants are the permission bits, and the macros check file types. Slay.
Constants
S_IRGRP, S_IROTH, S_IRUSR, S_IRWXG, S_IRWXO, S_IRWXU, S_ISGID, S_ISUID, S_IWGRP, S_IWOTH, S_IWUSR, S_IXGRP, S_IXOTH, S_IXUSR
Macros
S_ISBLK, S_ISCHR, S_ISDIR, S_ISFIFO, S_ISLNK, S_ISREG, S_ISSOCK
🧰 STDLIB 🧰
Standard library constants, the basics. EXIT_FAILURE and EXIT_SUCCESS are your exit codes, MB_CUR_MAX is for multibyte, and RAND_MAX is the biggest random number you can get from rand().
Constants
EXIT_FAILURE, EXIT_SUCCESS, MB_CUR_MAX, RAND_MAX
📝 STDIO 📝
Standard I/O constants, for buffering and file names and temp files. BUFSIZ is the buffer size, EOF is end of file, FILENAME_MAX is max filename length, L_ctermid and L_cuserid are for terminal and user id strings, and TMP_MAX is max temp files.
Constants
BUFSIZ, EOF, FILENAME_MAX, L_ctermid, L_cuserid, TMP_MAX
⏰ TIME ⏰
Time constants, for clock ticks and clock stuff. CLK_TCK is the number of clock ticks per second, and CLOCKS_PER_SEC is the number of clock ticks per second for clock().
Constants
CLK_TCK, CLOCKS_PER_SEC
🐚 UNISTD 🐚
Unix standard constants, for access checks and file seeking and standard file descriptors. R_OK, W_OK, X_OK are for access(), SEEK_CUR, SEEK_END, SEEK_SET are for lseek(), and STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO are the file descriptor numbers for standard input, output, and error.
Constants
R_OK, SEEK_CUR, SEEK_END, SEEK_SET, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO, W_OK, X_OK
👶 WAIT 👶
Wait constants and macros, for waiting on child processes. This is where you check exit statuses and signals. It's giving "parenting your processes".
Constants
WNOHANG, WUNTRACED
WNOHANG— Do not suspend the calling process until a child process changes state but instead return immediately.WUNTRACED— Catch stopped child processes.
Macros
WIFEXITED, WEXITSTATUS, WIFSIGNALED, WTERMSIG, WIFSTOPPED, WSTOPSIG
WIFEXITED—WIFEXITED(${^CHILD_ERROR_NATIVE})returns true if the child process exited normally (exit() or by falling off the end of main())WEXITSTATUS—WEXITSTATUS(${^CHILD_ERROR_NATIVE})returns the normal exit status of the child process (only meaningful ifWIFEXITED(${^CHILD_ERROR_NATIVE})is true)WIFSIGNALED—WIFSIGNALED(${^CHILD_ERROR_NATIVE})returns true if the child process terminated because of a signalWTERMSIG—WTERMSIG(${^CHILD_ERROR_NATIVE})returns the signal the child process terminated for (only meaningful ifWIFSIGNALED(${^CHILD_ERROR_NATIVE})is true)WIFSTOPPED—WIFSTOPPED(${^CHILD_ERROR_NATIVE})returns true if the child process is currently stopped (can happen only if you specified theWUNTRACEDflag towaitpid())WSTOPSIG—WSTOPSIG(${^CHILD_ERROR_NATIVE})returns the signal the child process was stopped for (only meaningful ifWIFSTOPPED(${^CHILD_ERROR_NATIVE})is true)
🪟 WINSOCK 🪟
(Windows only.) Winsock constants, for all your Windows socket error needs. Added in Perl v5.24, so they're relatively new. No cap.
Constants
Added in Perl v5.24:
WSAEINTR, WSAEBADF, WSAEACCES, WSAEFAULT, WSAEINVAL, WSAEMFILE, WSAEWOULDBLOCK, WSAEINPROGRESS, WSAEALREADY, WSAENOTSOCK, WSAEDESTADDRREQ, WSAEMSGSIZE, WSAEPROTOTYPE, WSAENOPROTOOPT, WSAEPROTONOSUPPORT, WSAESOCKTNOSUPPORT, WSAEOPNOTSUPP, WSAEPFNOSUPPORT, WSAEAFNOSUPPORT, WSAEADDRINUSE, WSAEADDRNOTAVAIL, WSAENETDOWN, WSAENETUNREACH, WSAENETRESET, WSAECONNABORTED, WSAECONNRESET, WSAENOBUFS, WSAEISCONN, WSAENOTCONN, WSAESHUTDOWN, WSAETOOMANYREFS, WSAETIMEDOUT, WSAECONNREFUSED, WSAELOOP, WSAENAMETOOLONG, WSAEHOSTDOWN, WSAEHOSTUNREACH, WSAENOTEMPTY, WSAEPROCLIM, WSAEUSERS, WSAEDQUOT, WSAESTALE, WSAEREMOTE, WSAEDISCON, WSAENOMORE, WSAECANCELLED, WSAEINVALIDPROCTABLE, WSAEINVALIDPROVIDER, WSAEPROVIDERFAILEDINIT, WSAEREFUSED
That's the whole page, bestie! You just read the POSIX(3perl) page from perl v5.44.0, dated 2026-10-17. Slay. 💅✨
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