POSIX(3pm)
🦋 NAME 🦋
POSIX(3pm) — from the Perl Programmers Reference Guide — is literally the Perl interface to IEEE Std 1003.1. That's the whole vibe, bestie. 💖
✨ SYNOPSIS ✨
Okay so here's the starter pack, no cap:
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 filehandle🌸 DESCRIPTION 🌸
The POSIX module permits you to access all (or nearly all) the standard POSIX 1003.1 identifiers. Many of these identifiers have been given Perl-ish interfaces. 🫶
This document gives a condensed list of the features available in the POSIX module. Consult your operating system's manpages for general information on most features. Consult perlfunc for functions which are noted as being identical or almost identical to Perl's builtin functions.
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. ✨
The notation [C99] indicates functions that were added in the ISO/IEC 9899:1999 version of the C language standard. Some may not be available on your system if it adheres to an earlier standard. Attempts to use any missing one will result in a fatal runtime error message. 😭
💅 CAVEATS 💅
Okay bestie, listen. Everything is exported by default (with a handful of exceptions). This is an unfortunate backwards compatibility feature and its use is strongly discouraged. You should 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. 💀
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". Not me getting a whole message about it, but okay. 🙈
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 define EDEADLK, or the semantics of the errno values set by open(2) might not be quite right. Perl does not attempt to verify POSIX compliance. That means you can currently successfully say use POSIX, and then later in your program you find that your vendor has been lax and there's no usable ICANON macro after all. This could be construed to be a bug. Periodt. 😭
🔥 FUNCTIONS 🔥
Here's the function roll call, in order, with all the deets. 💅
💀 _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 exception🔐 access
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. Do not ignore this one, bestie. 🚩
🌊 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 exception📅 asctime
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. 0️⃣
🔢 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 exception🔐 chmod
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 🎀
Makes a brand-new file, bestie. Hands you back a file descriptor, exactly like the ones POSIX::open gives you. Close it with POSIX::close when you're done, okay? Don't leave it hanging.
$fd = POSIX::creat( "foo", 0611 );
POSIX::close( $fd );Also go look at sysopen in perlfunc and its O_CREAT flag — same energy, different fit. ✨
ctermid 🦋
Spits out the path name for your controlling terminal. That's it, that's the whole job.
$path = POSIX::ctermid();ctime 💅
Literally identical to the C function ctime(), and it's equivalent to asctime(localtime(...)) — so go peek at asctime and localtime if you want the deets.
cuserid [POSIX.1-1988] 🌸
Gives you the login name of whoever owns the current process.
$name = POSIX::cuserid();heads up bestie: this one hasn't been specified by POSIX since 1990. It's only still here for backwards compatibility. New code should use getlogin() instead, no cap.
difftime ⭐
Identical to the C function difftime(). It returns the time difference, in seconds, between two times (the kind time() hands you). See time.
div 💀
Not implemented, sorry. div() is C-specific — use int in perlfunc on the usual / division, and the modulus %.
dup 🔥
Similar to the C function dup(), for duplicating a file descriptor.
This works with file descriptors like the ones you get from calling POSIX::open.
Returns undef on failure. 🫶
dup2 🔥
Similar to the C function dup2() — this one duplicates a file descriptor onto another known file descriptor.
Again, this 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.
$errno = POSIX::errno();This is identical to the numerical values of $! — see $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. See exit in perlfunc.
exp 🌈
Identical to Perl's builtin exp() function, which returns the exponent (e-based) of the numerical argument — except that POSIX::exp() has to be given an explicit value (no relying on an implicit $_, bestie):
$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 POSIX::fabs() must be given an explicit value (rather than relying on an implicit $_):
$absolute_value = POSIX::fabs(3); # good
$absolute_value = POSIX::fabs(); # throws exceptionSee abs in perlfunc.
okay so real talk — the source page has a stray leftover fragment right here: "This is identical to Perl's builtin cos() function for returning the cosine" — and then it immediately clips into thefcloseentry,=itemmarker and all. That's a page glitch, not a you problem. 🫶 Carrying on:
fclose 🎀
Not implemented. Use the method IO::Handle::close() instead, or see close in perlfunc.
fcntl 🦋
Identical to Perl's builtin fcntl() function, see fcntl in perlfunc.
fdopen 🦋
Not implemented. Use the method IO::Handle::new_from_fd() instead, or see open in perlfunc.
feof 🦋
Not implemented. Use the method IO::Handle::eof() instead, or see eof in perlfunc.
ferror 🦋
Not implemented. Use the method IO::Handle::error() instead.
fflush 🦋
Not implemented. Use the method IO::Handle::flush() instead. See also "$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() — returns the largest integer value less than or equal to the numerical argument.
fdim ✨
"Positive difference" — that'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 icons:
FE_TONEAREST FE_TOWARDZERO FE_UPWARD FE_DOWNWARDFE_TONEAREST is like round, 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 🔥
"Fused multiply-add" — x * y + z, possibly faster (and less lossy) than doing it as two explicit 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 has the same sign as $x and a magnitude (absolute value) less than the magnitude of $y. Math slay. ✨
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're on Windows.
fpathconf 🎀
Gets you the value of a configurable limit on a file or directory. This uses file descriptors such as those obtained by calling POSIX::open.
The following little number figures out the maximum length of the longest allowable pathname on the filesystem holding /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:
FP_NORMAL FP_ZERO FP_SUBNORMAL FP_INFINITE FP_NAN…telling you the class of the argument [C99]. FP_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, and 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 — it's giving main character energy, you don't have to micromanage it. 🫶
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.
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. (Yes, that's how the page says it. Copying it faithfully, bestie. 💅)
fstat 👑
Get file status. This uses file descriptors such as those obtained by calling POSIX::open. The data it returns 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 same information is available through the %ENV array too, iykyk.
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)Bestie, this one hands you back the "NaN" payload. It showed up in Perl v5.24 ✨
Heads up: peep the API instability warning over in "setpayload" before you get too attached 🙈
Also go read "nan" for the full tea on "NaN" 🫖
getpgrp
Literally the same as Perl's builtin getpgrp() — it gives you back the process group identifier of the current process. See "getpgrp" in perlfunc 💅
getpid
Returns the process identifier. It's identical to Perl's builtin variable $$, see "$PID" in perlvar 🎀
getppid
Same deal as Perl's builtin getppid(), except this one returns the process identifier of the parent process of the current process, see "getppid" in perlfunc 👑
getpwnam
Identical to Perl's builtin getpwnam(), which returns user entries by user names, see "getpwnam" in perlfunc 🦋
getpwuid
Identical to Perl's builtin getpwuid() — this one returns user entries by user identifiers, see "getpwuid" in perlfunc 🌸
gets
Returns one line from STDIN, kinda like <> — also known as the readline() function, see "readline" in perlfunc.
⚠️ OKAY SO. MAJOR PSA. 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. Like fr fr, do not do it 💀
getuid
Returns the user's identifier. Identical to Perl's builtin $< variable, see "$UID" in perlvar 💜
gmtime
Identical to Perl's builtin gmtime() function, which converts 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 way 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, no cap:
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
Gone as of Perl v5.24 😭 It was very similar to matching against qr/ ^ [[:alpha:]]+ $ /x, so convert to that 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
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
Also 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
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
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 ✨
Fun fact: you can also test for "NaN"-ness with the equality operators (== or !=), like this:
print "x is not a NaN\n" if $x == $x;That works because the "NaN" is not equal to anything, including itself 😭 iconic behaviour tbh.
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
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
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)Returns true if the argument is a signaling NaN. Added in Perl v5.24 ⭐
Same warning as before bestie — note the API instability warning in "setpayload" 🙈
See "nan" for more discussion about "NaN" 🍓
isspace
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
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
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 👑 (yes, all of these are listed together like that!)
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". Users of this function should also read perllocale, which provides a comprehensive discussion of Perl locale handling, including a section devoted to this function.
⚠️ Important caveat, listen up: 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. 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 were added by POSIX.1-2008 ✨ and they're only there on systems that actually support them — so don't come crying to me if they're missing, bestie 💅
A value of -1 coming back for a numeric entry means this field just doesn't apply to the locale 🫶 that's rare except in the C locale and its little cousins, which don't have most of the monetary values defined. and ngl it can also happen — quirkily 😭 — in fields that are otherwise boolean, to mean "this value is kind of neither true nor false". where does that pop up? in p_cs_precedes and int_p_cs_precedes, when the currency symbol neither precedes nor succeeds a positive value but is infixed 💀 — by replacing the radix character. wild, I know.
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 an ancient perl, pls don't go looking for keys that ghosted you 🙈
localtime
This is literally identical to Perl's builtin localtime() function for converting seconds-since-the-epoch into a date (see "localtime" in perlfunc) — except that POSIX::localtime() must be given an explicit value (aka no relying on the implicit $_, she's not doing that for you):
@localtime = POSIX::localtime(time); # good
@localtime = localtime(); # good
@localtime = POSIX::localtime(); # throws exceptionlog
Same vibe as Perl's builtin log() — returns the natural (e-based) logarithm of the numerical argument 🌱 — but again, POSIX::log() needs an explicit value, no implicit $_ shortcuts:
$log = POSIX::log(3); # good
$log = POSIX::log(); # throws exceptionSee "log" in perlfunc 🫶
log10
Identical to the C function log10(), returning the 10-base logarithm of the numerical argument 🔥 You can also just roll it yourself with
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, she ate and left no crumbs 👑
lseek
Moves the file's read/write position 📍 This one uses file descriptors, like the ones you get from 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, this 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 ✨
wanna know about the rounding mode? see "fegetround" 👀
lround
Like "round", but as an integer, as opposed to floating point [C99] 💅 Added in Perl v5.22 ✨
See also "ceil", "floor", "trunc" ⭐
ngl, owing to an oversight 🙈 this is not currently exported by default, nor as part of the ":math_h_c99" export tag — so importing it has to be done by explicit name, iykyk.
malloc
not implemented 😭 malloc() is C-specific. Perl does memory management transparently, she handles it, don't worry your pretty head about it 💖
mblen
Same as the C function mblen() on unthreaded perls 🧚 on threaded perls it transparently (almost) substitutes the more thread-safe "mbrlen(3)", if it's available, instead of "mblen" ✨
Core Perl does not have any support for wide and multibyte locales — except Unicode UTF-8 locales 🦋 This function, together with"mbtowc"and"wctomb", may be used to roll your own decoding/encoding of other types of multi-byte locales. main character DIY energy 👑
Use "undef" as the first parameter to get the effect of passing NULL as the first parameter to "mblen" — that resets any shift state to its initial value 🌀 The return value is undefined if "mbrlen" was substituted, so like... never rely on it, bestie 💀
When the first parameter is a scalar holding 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
0if that first character is the wide NUL character - or negative if there's an error 😭
This is based on the locale that currently underlies the program — regardless of whether the function is called from Perl code inside 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's larger than the actual length of the first parameter string 🙈
mbtowc
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 🦋 Together with"mblen"and"wctomb", this function 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 in the second parameter gets stored 🎀 The optional third parameter is ignored if it's larger than the actual length of the second parameter string.
Use "undef" as the second parameter 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 never ever rely on it 😭
When the second parameter is a scalar holding 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
0if that first character is the wide NUL character - or negative if there's 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 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
Identical to Perl's builtin mkdir() function for creating directories, see "mkdir" in perlfunc 📁✨
mkfifo
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 skipping it bestie 💅
mktime
Converts date/time info into 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) all begin at zero — like, 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 the 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
Returns 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 — she's not out here causing a scene 🙈
okay so continuing the nan tea ☕️ — with an argument, nan() can be used to generate a NaN with a payload. the argument is first interpreted as a floating point number, but 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.
the result has a dual nature: it's a NaN, but it also carries the integer inside it. the integer can be retrieved with getpayload. note, though, that 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.) 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
returns the nearest integer to the argument, according to the current rounding mode (see fegetround) [C99]. added in Perl v5.22. 🎯
nextafter
returns 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. 🙏
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 or writing. this returns file descriptors, not Perl filehandles. 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. 📂
$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. 📏
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. ⏸️
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. 🚨
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. 💥
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. 📖
$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. 🧠
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 an esoteric interface, mainly used to implement numerical algorithms.) 🧮
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 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. 👥
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. 🚨🧵
this function modifies and queries the program's underlying locale. users of this function should read perllocale, which 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 );The following will set the LC_CTYPE behaviour according to the locale environment variables (the second argument ""). Please see your system's setlocale(3) documentation for the locale environment variables' meaning, or consult perllocale 🧚
$loc = setlocale( LC_CTYPE, "" );The following will set the LC_COLLATE behaviour to Argentinian Spanish. NOTE: the naming and availability of locales depends on your operating system. Please consult perllocale for how to find out which locales are available in your system 💖
$loc = setlocale( LC_COLLATE, "es_AR.ISO8859-1" );setpayload 💅
use POSIX ':nan_payload';
setpayload($var, $payload);Sets the NaN payload of var. Added in Perl v5.24.
NOTE: the NaN payload APIs are based on the latest (as of June 2015) proposed ISO C interfaces, but they are not yet a standard. Things may change. So like… don't build your whole personality on them yet 😭
See "nan" for more discussion about NaN.
See also "setpayloadsig", "isnan", "getpayload", and "issignaling".
setpayloadsig ✨
use POSIX ':nan_payload';
setpayloadsig($var, $payload);Like "setpayload" but also makes the NaN signaling. Added in Perl v5.24.
Depending on the platform the NaN may or may not behave differently.
Note the API instability warning in "setpayload" 👀
Note that because of how the floating point formats work out, on the most common platforms a signaling payload of zero is best avoided, since it might end up being identical to +Inf 💀
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.
Returns undef on failure.
setsid 🌸
This is identical to the C function setsid() for setting the session identifier of the current process.
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. Iconic difference, lowkey important 💅
sigaction 🚨
Detailed signal management. This uses POSIX::SigAction objects for the action and oldaction arguments (the oldaction can also be just a hash reference). Consult your system's sigaction manpage for details, 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 hard to understand you 😭 bless it.
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 are 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 a Perl perspective — you should consult your system's sigaction and possibly also siginfo documentation.
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 🦋
Examine 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. Fr fr, don't fight it 💀
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, for returning the sine of its numerical argument — except that POSIX::sin() must be provided with an explicit value (rather than relying on an implicit $_):
$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. There is one significant difference, however: POSIX::sleep() returns the number of unslept seconds, while CORE::sleep() returns the number of slept seconds. Sneaky little plot twist, iykyk 👀
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 provided with 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.
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 transformed using the strxfrm() function. Not really needed since Perl can do this transparently, see perllocale.
Beware that 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. No mixing, bestie 🙈
Note also that 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). The results will be essentially meaningless. It's giving chaos for no reason 😭
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, so they really said "why are you even here" 💅
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 🎀
Nope, not implemented bestie. strrchr() is C-specific — slide over to rindex in perlfunc instead. 💅
strspn 🎀
Also not implemented. strspn() is C-specific, so use regular expressions instead, see perlre. ✨
strstr 🎀
Okay so this one is literally identical to Perl's builtin index() function, see index in perlfunc. Slay. 👑
strtod 🎀
String to double translation, periodt. 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. However — and this is the messy part 🙈 — 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. 😭
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 — use regular expressions instead, see perlre, or split in perlfunc. 💀
strtol 🎀
String to (long) integer translation, iconic behavior honestly. 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. But again, 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 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. Fancy. 🌸
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. Returns the transformed string. 🦋
$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:
$clock_ticks = POSIX::sysconf( &POSIX::_SC_CLK_TCK );Returns undef on failure. 😭
system 🎀
Identical to Perl's builtin system() function, see system in perlfunc. 💅
tan 🎀
Identical to the C function tan(), returning the tangent of the numerical argument. See also Math::Trig. 📐
tanh 🎀
Identical to the C function tanh(), returning the hyperbolic tangent of the numerical argument. See also Math::Trig. 📐
tcdrain 🎀
This is similar to the C function tcdrain() for draining the output queue of its argument stream.
Returns undef on failure. 🌊
tcflow 🎀
This is similar to the C function tcflow() for controlling the flow of its argument stream.
Returns undef on failure. 🌊
tcflush 🎀
This is similar to the C function tcflush() for flushing the I/O buffers of its argument stream.
Returns undef on failure. 🌊
tcgetpgrp 🎀
Identical to the C function tcgetpgrp() for returning the process group identifier of the foreground process group of the controlling terminal. 👑
tcsendbreak 🎀
This is similar to the C function tcsendbreak() for sending a break on its argument stream.
Returns undef on failure. 💔
tcsetpgrp 🎀
This is similar to the C function tcsetpgrp() for setting the process group identifier of the foreground process group of the controlling terminal.
Returns undef on failure. 😤
tgamma 🎀
The Gamma function [C99]. Added in Perl v5.22. ✨
See also lgamma.
time 🎀
Identical to Perl's builtin time() function for returning the number of seconds since the epoch (whatever it is for the system), see time in perlfunc. ⏰
times 🎀
The times() function returns elapsed realtime since some point in the past (such as system startup), user and system times for this process, and user and system times used by child processes. All times are returned in clock ticks. 🕰️
($realtime, $user, $system, $cuser, $csystem)
= POSIX::times();Note: Perl's builtin times() function returns four values, measured in seconds. Don't mix them up bestie 😭
tmpfile 🎀
Not implemented. Use method IO::File::new_tmpfile() instead, or see File::Temp. 🗂️
tmpnam 🎀
For security reasons — which are probably detailed in your system's documentation for the C library tmpnam() function — this interface is no longer available since Perl v5.26; instead use File::Temp. 🔒
tolower 🎀
This function has been removed as of Perl v5.26. It's identical to the C function, except that it can apply to a single character or to a whole string, and currently operates as if the locale always is C. Consider using the lc() function, see lc in perlfunc, see lc in perlfunc, or the equivalent \L operator inside doublequotish strings. 💅
toupper 🎀
This function has been removed as of Perl v5.26. It's similar to the C function, except that it can apply to a single character or to a whole string, and currently operates as if the locale always is C. Consider using the uc() function, see uc in perlfunc, or the equivalent \U operator inside doublequotish strings. 💅
trunc 🎀
Returns the integer toward zero from the argument [C99]. Added in Perl v5.22. ✨
See also ceil, floor, and round.
ttyname 🎀
Identical to the C function ttyname() for returning the name of the current terminal. 🖥️
tzname 🎀
Retrieves the time conversion information from the tzname variable. 🌍
POSIX::tzset();
($std, $dst) = POSIX::tzname();tzset 🎀
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 🎀
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, $machine)
= POSIX::uname();Note that the actual meanings of the various fields are not that well standardized, do not expect any great portability. The$sysnamemight be the name of the operating system, the$nodenamemight be the name of the host, the$releasemight be the (major) release number of the operating system, the$versionmight be the (minor) release number of the operating system, and the$machinemight be a hardware identifier. Maybe. 🙈
ungetc 🎀
Not implemented. Use method IO::Handle::ungetc() instead. 💅
unlink 🎀
Identical to Perl's builtin unlink() function for removing files, see unlink in perlfunc. 🗑️
utime 🎀
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 🎀
Identical to Perl's builtin wait() function, see wait in perlfunc. ⏳
waitpid ⏳
okay so waitpid is literally just your "hey bestie, has the child process changed state yet?" check — and it's identical to Perl's builtin waitpid() function, so go read "waitpid" in perlfunc for the full lore. 👀
$pid = POSIX::waitpid( -1, POSIX::WNOHANG );
print "status = ", ($? / 256), "\n";See "mblen".
wctomb 🔤
On unthreaded perls this is exactly the same as the C function wctomb(). On threaded perls, though, it transparently (almost) swaps in the much more thread-safe "wcrtomb(3)" instead of "wctomb", if that's available. ✨
Big vibe check: Core Perl does not have any support for wide and multibyte locales — except Unicode UTF-8 locales. So this function, hanging out with"mblen"and"mbtowc", is how you roll your own decoding/encoding for other types of multi-byte locales. 🎲
- Pass
undefas the first parameter and you get the effect of passing NULL as the first parameter to"wctomb". This ignores the second parameter and resets any shift state to its initial value. The return value is undefined if"wcrtomb"was 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 the first parameter scalar. This is based on the locale that currently underlies the program — 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. - Perl makes no attempt at hiding from your code any differences in the
errnosetting between"wctomb"and"wcrtomb". It does seterrnoto0before calling them. 🫶
write ✍️
Write to a file — using file descriptors like the ones you snag by calling "POSIX::open". iconic behavior, honestly.
$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 a brand-newPOSIX::SigActionobject, and it's literally the Perl twin of the Cstruct sigaction. She gets destroyed automatically the moment nobody needs her anymore, so no cleanup stress 💅. First param = the handler, and it's a sub reference. Second param = aPOSIX::SigSetobject, and it defaults to the empty set. Third param = thesa_flags, defaulting to0.
$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 her whole job, iykyk.
handler,mask,flags— accessor functions to get/set the values of a SigAction object. Very main-character energy for someone who just wants to peek and poke.
$sigset = $sigaction->mask;
$sigaction->flags(&POSIX::SA_RESTART);safe— accessor function for the "safe signals" flag of a SigAction object; peepperlipcfor the general lore on safe (a.k.a. "deferred") signals. If you want to handle a signal safely, use this accessor to set thesafeflag in thePOSIX::SigActionobject:
$sigaction->safe(1);You can also examine the safe flag on the output action object, which 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, and it's basically an extension of the standard%SIG. Like,$POSIX::SIGRT{SIGRTMIN}is roughly equivalent to$SIG{SIGRTMIN}, except the right POSIX moves get made (see below) with thePOSIX::SigSetandPOSIX::sigactioninstead of touching%SIGdirectly. So much more civilized tbh.
You can set the %POSIX::SIGRT elements to set the POSIX realtime signal handlers, use delete and exists on the elements, and slap scalar on %POSIX::SIGRT to find out how many POSIX realtime signals are available (SIGRTMAX - SIGRTMIN + 1 — and heads up, 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 can either use local on $POSIX::SigRt::SIGACTION_FLAGS, or you can derive from POSIX::SigRt and define your own new() (the tied hash STORE method of the %SIGRT calls new($rtsig, $handler, $SIGACTION_FLAGS), where the $rtsig ranges from zero to SIGRTMAX - SIGRTMIN + 1)).
Just like with any signal, you can use sigaction($rtsig, undef, $oa) to retrieve the installed signal handler (or, more accurately, the signal action). Retrieval era ✨.
NOTE: whether POSIX realtime signals actually work on your system, or whether Perl has been compiled so that it works with them — that's outside of this discussion, bestie. Don't shoot the messenger 🙈.
SIGRTMIN— returns the minimum POSIX realtime signal number available, orundefif there are no POSIX realtime signals available. She's either there or she's not 🫶.SIGRTMAX— returns the maximum POSIX realtime signal number available, orundefif there are no POSIX realtime signals available. Same deal 💜.
POSIX::SigSet
new— creates a new SigSet object. It gets destroyed automatically once it's not needed anymore, no cap. You can pass arguments to initialize the set.
Create an empty set:
$sigset = POSIX::SigSet->new;Create a set with SIGUSR1:
$sigset = POSIX::SigSet->new( &POSIX::SIGUSR1 );And it throws an error if any of the signals you supplied can't be added to the set. Rude, but fair.
addset— adds a signal to a SigSet object.
$sigset->addset( &POSIX::SIGUSR2 );Returns undef on failure.
delset— removes a signal from the SigSet object. Bye bestie 👋.
$sigset->delset( &POSIX::SIGUSR2 );Returns undef on failure.
emptyset— initializes the SigSet object to be empty. Empty-set vibes, honestly iconic.
$sigset->emptyset();Returns undef on failure.
fillset— initializes the SigSet object to include all signals. She contains multitudes.
$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— creates a new Termios object, and yeah, she's destroyed automatically when she's not needed anymore. A Termios object corresponds to thetermiosC struct.new()mallocs a new one,getattr()fills it from a file descriptor, andsetattr()sets a file descriptor's parameters to match Termios' contents. Full glow-up cycle 💅.
$termios = POSIX::Termios->new;getattr— gets 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— retrieves a value from thec_ccfield of atermiosobject. Thec_ccfield is an array, so an index must be specified. No index, no entry 🔥.
$c_cc[1] = $termios->getcc(1);getcflag— retrieves thec_cflagfield of atermiosobject.
$c_cflag = $termios->getcflag;getiflag— retrieves thec_iflagfield of atermiosobject.
$c_iflag = $termios->getiflag;getispeed— retrieves the input baud rate.
$ispeed = $termios->getispeed;getlflag— retrieves thec_lflagfield of atermiosobject.
$c_lflag = $termios->getlflag;getoflag— retrieves thec_oflagfield of atermiosobject.
$c_oflag = $termios->getoflag;getospeed— retrieves the output baud rate.
$ospeed = $termios->getospeed;setattr— sets terminal control attributes.
Set attributes immediately for stdout:
$termios->setattr( 1, &POSIX::TCSANOW );Returns undef on failure.
setcc— sets a value in thec_ccfield of atermiosobject. Thec_ccfield is an array, so an index must be specified.
$termios->setcc( &POSIX::VEOF, 1 );setcflag— sets thec_cflagfield of atermiosobject.
$termios->setcflag( $c_cflag | &POSIX::CLOCAL );setiflag— sets thec_iflagfield of atermiosobject.
$termios->setiflag( $c_iflag | &POSIX::BRKINT );setispeed— sets the input baud rate.
$termios->setispeed( &POSIX::B9600 );Returns undef on failure.
setlflag— sets thec_lflagfield of atermiosobject.
$termios->setlflag( $c_lflag | &POSIX::ECHO );setoflag— sets thec_oflagfield of atermiosobject.
$termios->setoflag( $c_oflag | &POSIX::OPOST );setospeed— sets the output baud rate.
$termios->setospeed( &POSIX::B9600 );Returns undef on failure.
Baud rate values
B38400 B75 B200 B134 B300 B1800 B150 B0 B19200 B1200 B9600 B600 B4800 B50 B2400 B110
Terminal interface values
TCSADRAIN TCSANOW TCOON TCIOFLUSH TCOFLUSH TCION TCIFLUSH TCSAFLUSH TCIOFF TCOOFF
c_cc field values
VEOF VEOL VERASE VINTR VKILL VQUIT VSUSP VSTART VSTOP VMIN VTIME NCCS
c_cflag field values
CLOCAL CREAD CSIZE CS5 CS6 CS7 CS8 CSTOPB HUPCL PARENB PARODD
c_iflag field values
BRKINT ICRNL IGNBRK IGNCR IGNPAR INLCR INPCK ISTRIP IXOFF IXON PARMRK
c_lflag field values
ECHO ECHOE ECHOK ECHONL ICANON IEXTEN ISIG NOFLSH TOSTOP
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. Gatekept no more 🫶.
Constants
Added in Perl v5.28:
PRIO_PROCESS PRIO_PGRP PRIO_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 errno constants are giving “every possible plot twist” energy 😭 — here are the exact names, no cap, don’t freestyle them:
E2BIG,EACCES,EADDRINUSE,EADDRNOTAVAIL,EAFNOSUPPORT,EAGAIN,EALREADY,EBADF,EBADMSG,EBUSY,ECANCELEDECHILD,ECONNABORTED,ECONNREFUSED,ECONNRESET,EDEADLK,EDESTADDRREQ,EDOM,EDQUOT,EEXIST,EFAULT,EFBIGEHOSTDOWN,EHOSTUNREACH,EIDRM,EILSEQ,EINPROGRESSEINTR,EINVAL,EIO,EISCONN,EISDIR,ELOOP,EMFILE,EMLINKEMSGSIZE,ENAMETOOLONG,ENETDOWN,ENETRESET,ENETUNREACH,ENFILE,ENOBUFS,ENODATA,ENODEV,ENOENTENOEXEC,ENOLCK,ENOLINK,ENOMEM,ENOMSG,ENOPROTOOPT,ENOSPC,ENOSR,ENOSTR,ENOSYS,ENOTBLK,ENOTCONNENOTDIR,ENOTEMPTY,ENOTRECOVERABLE,ENOTSOCK,ENOTSUP,ENOTTY,ENXIO,EOPNOTSUPP,EOTHER,EOVERFLOW,EOWNERDEADEPERM,EPFNOSUPPORT,EPIPE,EPROCLIM,EPROTO,EPROTONOSUPPORT,EPROTOTYPE,ERANGE,EREMOTE,ERESTARTEROFS,ESHUTDOWN,ESOCKTNOSUPPORT,ESPIPE,ESRCH,ESTALE,ETIME,ETIMEDOUT,ETOOMANYREFS,ETXTBSY,EUSERSEWOULDBLOCK,EXDEV
🔐 FCNTL 🔐
fcntl constants, bestie — file-control-flavored, exact spellings only 💅:
💖 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!! these are literally the math-y little guys 🧚:
✨ 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 🎀
the floating-point environment constants — here’s the exact set:
🌸 Constants 🌸
FE_DOWNWARD,FE_TONEAREST,FE_TOWARDZERO,FE_UPWARDon systems that support them.
🚧 LIMITS 🚧
limits constants — these are the “how much can we push it” besties 🔥:
💜 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 — little cultural vibe-check switches, iykyk 🦋:
🌈 Constants 🌈
LC_ALL,LC_COLLATE,LC_CTYPE,LC_MONETARY,LC_NUMERIC,LC_TIME,LC_MESSAGESon systems that support them.
🧮 MATH 🧮
math constants, bestie — yes there is exactly one first, and then a v5.22 glow-up ✨:
💫 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_SQRT2on systems with C99 support.
🚨 SIGNAL 🚨
signal constants — the “something is happening and you need to know” lineup 💀:
⭐ 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 — file-status besties, periodt 🫶:
🎀 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 — small but iconic 👑:
🌟 Constants 🌟
EXIT_FAILURE,EXIT_SUCCESS,MB_CUR_MAX,RAND_MAX
🖨️ STDIO 🖨️
stdio constants — input/output-flavored little guys 🍓:
💖 Constants 💖
BUFSIZ,EOF,FILENAME_MAX,L_ctermid,L_cuserid,TMP_MAX
⏰ TIME ⏰
time constants — clock girlies, we love you ⏳:
✨ Constants ✨
CLK_TCK,CLOCKS_PER_SEC
🧚 UNISTD 🧚
unistd constants — the exact set, no skips, no cap:
🌸 Constants 🌸
R_OK,SEEK_CUR,SEEK_END,SEEK_SET,STDIN_FILENO,STDOUT_FILENO,STDERR_FILENO,W_OK,X_OK
👶 WAIT 👶
wait constants and macros — child-process-watching era 😭:
💜 Constants 💜
WNOHANG— Do not suspend the calling process until a child process changes state but instead return immediately.WUNTRACED— Catch stopped child processes.
🎀 Macros 🎀
WIFEXITED—WIFEXITED(${^CHILD_ERROR_NATIVE})returns true if the child process exited normally (exit()or by falling off the end ofmain())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.)
🖥️ 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
and that’s a wrap on the POSIX(3pm) page, bestie 🫶 — source/version: perl v5.42.3, date: 2026-11-03. mwah 💋✨
📦 where this page comes from
- alpine 3.24: perl-doc 5.42.3-r0 · Artistic-1.0-Perl OR GPL-1.0-or-later
- 💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on : a language model's rewrite of the original, under its terms