EDITLINE(3)

📦
version 20210910.3.1 · 10 versions
, in opensuse-leap 16.0

💅 editline(3) — line editor, history & tokenization 🎀

okay bestie, this is the editline(3) page from the Library Functions Manual, and it’s giving “your terminal can do slay tricks” energy. Buckle up 💖

🌸 NAME 🌸

editline, el_init, el_init_fd, el_end, el_reset, el_gets, el_wgets, el_getc, el_wgetc, el_push, el_wpush, el_parse, el_wparse, el_set, el_wset, el_get, el_wget, el_source, el_resize, el_cursor, el_line, el_wline, el_insertstr, el_winsertstr, el_deletestr, el_wdeletestr, history_init, history_winit, history_end, history_wend, history, history_w, tok_init, tok_winit, tok_end, tok_wend, tok_reset, tok_wreset, tok_line, tok_wline, tok_str, tok_wstr — line editor, history and tokenization functions ✨

🎀 LIBRARY 🎀

Command Line Editor Library (libedit, -ledit) 🫶

✨ SYNOPSIS ✨

#include <histedit.h>

EditLine *
el_init(const char *prog, FILE *fin, FILE *fout, FILE *ferr);

EditLine *
el_init_fd(const char *prog, FILE *fin, FILE *fout, FILE *ferr, int
fdin, int fdout, int fderr);

void
el_end(EditLine *e);

void
el_reset(EditLine *e);

const char *
el_gets(EditLine *e, int *count);

const wchar_t *
el_wgets(EditLine *e, int *count);

int
el_getc(EditLine *e, char *ch);

int
el_wgetc(EditLine *e, wchar_t *wc);

void
el_push(EditLine *e, const char *mbs);

void
el_wpush(EditLine *e, const wchar_t *wcs);

int
el_parse(EditLine *e, int argc, const char *argv[]);

int
el_wparse(EditLine *e, int argc, const wchar_t *argv[]);

int
el_set(EditLine *e, int op, ...);

int
el_wset(EditLine *e, int op, ...);

int
el_get(EditLine *e, int op, ...);

int
el_wget(EditLine *e, int op, ...);

int
el_source(EditLine *e, const char *file);

void
el_resize(EditLine *e);

int
el_cursor(EditLine *e, int count);

const LineInfo *
el_line(EditLine *e);

const LineInfoW *
el_wline(EditLine *e);

int
el_insertstr(EditLine *e, const char *str);

int
el_winsertstr(EditLine *e, const wchar_t *str);

void
el_deletestr(EditLine *e, int count);

void
el_wdeletestr(EditLine *e, int count);

History *
history_init(void );

HistoryW *
history_winit(void );

void
history_end(History *h);

void
history_wend(HistoryW *h);

int
history(History *h, HistEvent *ev, int op, ...);

int
history_w(HistoryW *h, HistEventW *ev, int op, ...);

Tokenizer *
tok_init(const char *IFS);

TokenizerW *
tok_winit(const wchar_t *IFS);

void
tok_end(Tokenizer *t);

void
tok_wend(TokenizerW *t);

void
tok_reset(Tokenizer *t);

void
tok_wreset(TokenizerW *t);

int
tok_line(Tokenizer *t, const LineInfo *li, int *argc, const char
**argv[], int *cursorc, int *cursoro);

int
tok_wline(TokenizerW *t, const LineInfoW *li, int *argc, const wchar_t
**argv[], int *cursorc, int *cursoro);

int
tok_str(Tokenizer *t, const char *str, int *argc, const char **argv[]);

int
tok_wstr(TokenizerW *t, const wchar_t *str, int *argc, const wchar_t
**argv[]);

💖 DESCRIPTION 💖

The editline library hands you generic line editing, history and tokenization functions, similar to those found in sh(1). ✅

These functions live in the libedit library (which needs the libtermcap library). Programs should be linked with -ledit ltermcap 🫶

The editline library respects the LC_CTYPE locale set by the application program and never uses setlocale(3) to change the locale. no cap 💅

🦋 LINE EDITING FUNCTIONS 🦋

The line editing functions use a common data structure, EditLine, which is created by el_init() or el_init_fd() and freed by el_end().

The wide-character functions behave the same way as their narrow counterparts ✨

The following functions are available:

el_init() — Initialize the line editor, and return a data structure to be used by all other line editing functions, or NULL on failure. prog is the name of the invoking program, used when reading the editrc(5) file to determine which settings to use. fin, fout and ferr are the input, output, and error streams (respectively) to use. In this documentation, references to ``the tty'' are actually to this input/output stream combination. 🎀

el_init_fd() — Like el_init() but allows specifying file descriptors for the stdio(3) corresponding streams, in case those were created with funopen(3). 🧚

el_end() — Clean up and finish with e, assumed to have been created with el_init() or el_init_fd().

el_reset() — Reset the tty and the parser. This should be called after an error which may have upset the tty’s state. 🩹

el_gets() — Read a line from the tty. count is modified to contain the number of characters read. Returns the line read if successful, or NULL if no characters were read or if an error occurred. If an error occurred, count is set to -1 and errno contains the error code that caused it. The return value may not remain valid across calls to el_gets() and must be copied if the data is to be retained. 📌

el_wgetc() — Read a wide character from the tty, respecting the current locale, or from the input queue described in editline(7) if that is not empty, and store it in wc. If an invalid or incomplete character is found, it is discarded, errno is set to EILSEQ, and the next character is read and stored in wc. Returns 1 if a valid character was read, 0 on end of file, or -1 on read(2) failure. In the latter case, errno is set to indicate the error. 💀

el_getc() — Read a wide character as described for el_wgetc() and return 0 on end of file or -1 on failure. If the wide character can be represented as a single-byte character, convert it with wctob(3), store the result in ch, and return 1; otherwise, set errno to ERANGE and return -1. In the C or POSIX locale, this simply reads a byte, but for any other locale, including UTF-8, this is rarely useful. 🫠

el_wpush() — Push the wide character string wcs back onto the input queue described in editline(7). If the queue overflows, for example due to a recursive macro, or if an error occurs, for example because wcs is NULL or memory allocation fails, the function beeps at the user, but does not report the problem to the caller. 🔔

el_push() — Use the current locale to convert the multibyte string mbs to a wide character string, and pass the result to el_wpush().

el_parse() — Parses the argv array (which is argc elements in size) to execute builtin editline commands. If the command is prefixed with prog : then el_parse() will only execute the command if prog matches the prog argument supplied to el_init(). The return value is -1 if the command is unknown, 0 if there was no error or prog didn’t match, or 1 if the command returned an error. Refer to editrc(5) for more information. 🧾

el_set() — Set editline parameters. op determines which parameter to set, and each operation has its own parameter list. Returns 0 on success, -1 on failure. 🛠️

The following values for op are supported, along with the required argument list:

  • EL_PROMPT, char *(*f)(EditLine *) — Define prompt printing function as f, which is to return a string that contains the prompt.
  • EL_PROMPT_ESC, char *(*f)(EditLine *), char c — Same as EL_PROMPT, but the c argument indicates the start/stop literal prompt character.

If a start/stop literal character is found in the prompt, the character itself is not printed, but characters after it are printed directly to the terminal without affecting the state of the current line. A subsequent second start/stop literal character ends this behavior. This is typically used to embed literal escape sequences that change the color/style of the terminal in the prompt.

⚠️ Note that the literal escape character cannot be the last character in the prompt, as the escape sequence is attached to the next character in the prompt. 0 unsets it.
  • EL_REFRESH — Re-display the current line on the next terminal line. 🔄
  • EL_RPROMPT, char *(*f)(EditLine *) — Define right side prompt printing function as f, which is to return a string that contains the prompt.
  • EL_RPROMPT_ESC, char *(*f)(EditLine *), char c — Define the right prompt printing function but with a literal escape character.
  • EL_TERMINAL, const char *type — Define terminal type of the tty to be type, or to TERM if type is NULL.
  • EL_EDITOR, const char *mode — Set editing mode to mode, which must be one of emacs'' or vi''. 💻
  • EL_SIGNAL, int flag — If flag is non-zero, editline will install its own signal handler for the following signals when reading command input: SIGCONT, SIGHUP, SIGINT, SIGQUIT, SIGSTOP, SIGTERM, SIGTSTP, and SIGWINCH. Otherwise, the current signal handlers will be used. 🚨
  • EL_BIND, const char *, ..., NULL — Perform the bind builtin command. Refer to editrc(5) for more information.
  • EL_ECHOTC, const char *, ..., NULL — Perform the echotc builtin command. Refer to editrc(5) for more information.
  • EL_SETTC, const char *, ..., NULL — Perform the settc builtin command. Refer to editrc(5) for more information.
  • EL_SETTY, const char *, ..., NULL — Perform the setty builtin command. Refer to editrc(5) for more information.
  • EL_TELLTC, const char *, ..., NULL — Perform the telltc builtin command. Refer to editrc(5) for more information.
  • EL_ADDFN, const char *name, const char *help, unsigned char (*func)(EditLine *e, int ch) — Add a user defined function, func(), referred to as name which is invoked when a key which is bound to name is entered. help is a description of name. At invocation time, ch is the key which caused the invocation. The return value of func() should be one of:

CC_NORM — add a normal character. Very “just a lil guy” of you 💅

  • CC_NEWLINE — end of line was entered.
  • CC_EOF — EOF was entered.
  • CC_ARGHACK — expecting further command input as arguments, do nothing visually.
  • CC_REFRESH — refresh display.
  • CC_REFRESH_BEEP — refresh display, and beep.
  • CC_CURSOR — cursor moved, so update and perform CC_REFRESH.
  • CC_REDISPLAY — redisplay the entire input line. This is useful if a key binding outputs extra information.
  • CC_ERROR — an error occurred. Beep, and flush tty.
  • CC_FATAL — fatal error, reset tty to known state.

okay so the EL_* knobs keep rolling, and they are lowkey the main character energy of el_set():

  • EL_HIST, History *(*func)(History *, int op, ...), Fa "const char *ptr" — defines which history function to use, which is usually history(). ptr should be the value returned by history_init().
  • EL_EDITMODE, int flag — if flag is non-zero, editing is enabled (the default). Note that this is only an indication, and does not affect the operation of . — yes, the original has that floating period, iconic 😭 — at this time, it is the caller's responsibility to check this (using el_get()) to determine if editing should be enabled or not.
  • EL_UNBUFFERED, int flag — if flag is zero, unbuffered mode is disabled (the default). In unbuffered mode, el_gets() will return immediately after processing a single character.
  • EL_SAFEREAD, int flag — if the flag argument is non-zero, then editline attempts to recover from read errors, ignoring the first interrrupted error, and trying to reset the input file descriptor to reset non-blocking I/O. This is disabled by default, and desirable only when editline is used in shell-like applications.
  • EL_GETCFN, el_rfunc_t f — whenever reading a character, use the function. The manpage source drops -ragged -offset indent -compact on you (yes, the -ragged -offset -compact trio is literally in there 💀) and gives this signature:
int
Fo f EditLine *e wchar_t *wc Fc

which stores the character in wc and returns 1 on success, 0 on end of file, or -1 on I/O or encoding errors. Functions internally using it include el_wgets(), el_wgetc(), el_gets(), and el_getc(). Initially, a builtin function is installed, and replacing it is discouraged because writing such a function is very error prone. The builtin function can be restored at any time by passing the special value EL_BUILTIN_GETCFN instead of a function pointer.

  • EL_CLIENTDATA, void *data — register data to be associated with this EditLine structure. It can be retrieved with the corresponding el_get(); call.
  • EL_SETFP, int fd, Fa FILE *fp — set the current editline file pointer for input'' `fd = 0`, output'' fd = 1, or ``error'' fd = 2 from fp.

💜 el_get() — get the deets 💜

Get editline parameters. op determines which parameter to retrieve into result. Returns 0 if successful, -1 otherwise.

The following values for op are supported, along with actual type of result:

  • EL_PROMPT, char *(*f)(EditLine *), Fa char *c — set f to a pointer to the function that displays the prompt. If c is not NULL, set it to the start/stop literal prompt character.
  • EL_RPROMPT, char *(*f)(EditLine *), Fa char *c — set f to a pointer to the function that displays the prompt. If c is not NULL, set it to the start/stop literal prompt character.
  • EL_EDITOR, const char **n — set the name of the editor in n, which will be one of emacs'' or vi''.
  • EL_GETTC, const char *name, Fa void *value — if name is a valid termcap(5) capability set value to the current value of that capability.
  • EL_SIGNAL, int *s — set s to non-zero if editline has installed private signal handlers (see el_get() above).
  • EL_EDITMODE, int *c — set c to non-zero if editing is enabled.
  • EL_GETCFN, el_rfunc_t *f — set f to a pointer to the function that reads characters, or to EL_BUILTIN_GETCFN if the builtin function is in use.
  • EL_CLIENTDATA, void **data — set data to the previously registered client data set by an el_set() call.
  • EL_UNBUFFERED, int *c — set c to non-zero if unbuffered mode is enabled.
  • EL_SAFEREAD, int *c — set c to non-zero if safe read is set.
  • EL_GETFP, int fd, Fa FILE **fp — set fp to the current editline file pointer for input'' `fd = 0`, output'' fd = 1, or ``error'' fd = 2.

🦋 el_source() 🦋

Initialize editline by reading the contents of file. el_parse() is called for each line in file. If file is NULL, try $EDITRC and if that is not set $HOME/.editrc. Refer to editrc(5) for details on the format of file. el_source() returns 0 on success and -1 on error.

🌈 el_resize() 🌈

Must be called if the terminal size changes. If EL_SIGNAL has been set with el_set(), then this is done automatically. Otherwise, it's the responsibility of the application to call el_resize() on the appropriate occasions.

⭐ el_cursor() ⭐

Move the cursor to the right (if positive) or to the left (if negative) count characters. Returns the resulting offset of the cursor from the beginning of the line.

🎀 el_line() 🎀

Return the editing information for the current line in a LineInfo structure, which is defined as follows:

typedef struct lineinfo {
    const char *buffer;    /* address of buffer */
    const char *cursor;    /* address of cursor */
    const char *lastchar;  /* address of last character */
} LineInfo;

buffer is not NUL terminated. This function may be called after el_gets() to obtain the LineInfo structure pertaining to line returned by that function, and from within user defined functions added with EL_ADDFN.

🌸 el_insertstr() and el_deletestr() 🌸

el_insertstr() — insert str into the line at the cursor. Returns -1 if str is empty or won't fit, and 0 otherwise.

el_deletestr() — delete count characters before the cursor.

💖 HISTORY LIST FUNCTIONS 💖

Okay bestie, the history functions all share one common data structure, History, which is created by history_init() and freed by history_end(). That's the vibe check before the function roll call.

The following functions are available:

  • history_init() — Initialize the history list, and return a data structure to be used by all other history list functions, or NULL on failure. Slay, but check for NULL, fr fr.
  • history_end() — Clean up and finish with h, assumed to have been created with history_init().
  • history() — Perform operation op on the history list, with optional arguments as needed by the operation. ev is changed accordingly to operation. The following values for op are supported, along with the required argument list:
    • H_SETSIZE, int size — Set size of history to size elements.
    • H_GETSIZE — Get number of events currently in history.
    • H_END — Cleans up and finishes with h, assumed to be created with history_init().
    • H_CLEAR — Clear the history.
    • H_FUNC, void *ptr, history_gfun_t first, history_gfun_t next, history_gfun_t last, history_gfun_t prev, history_gfun_t curr, history_sfun_t set, history_vfun_t clear, history_efun_t enter, history_efun_t add — Define functions to perform various history operations. ptr is the argument given to a function when it's invoked.
    • H_FIRST — Return the first element in the history.
    • H_LAST — Return the last element in the history.
    • H_PREV — Return the previous element in the history. It is newer than the current one.
    • H_NEXT — Return the next element in the history. It is older than the current one.
    • H_CURR — Return the current element in the history.
    • H_SET, int position — Set the cursor to point to the requested element.
    • H_ADD, const char *str — Append str to the current element of the history, or perform the H_ENTER operation with argument str if there is no current element.
    • H_APPEND, const char *str — Append str to the last new element of the history.
    • H_ENTER, const char *str — Add str as a new element to the history and, if necessary, remove the oldest entry to keep the list to the created size. If H_SETUNIQUE has been called with a non-zero argument, the element will not be entered into the history if its contents match the ones of the current history element. If the element is entered history() returns 1; if it is ignored as a duplicate returns 0. Finally history() returns -1 if an error occurred. So yes, this one has receipts: 1, 0, or -1.
    • H_PREV_STR, const char *str — Return the closest previous event that starts with str.
    • H_NEXT_STR, const char *str — Return the closest next event that starts with str.
    • H_PREV_EVENT, int e — Return the previous event numbered e.
    • H_NEXT_EVENT, int e — Return the next event numbered e.
    • H_LOAD, const char *file — Load the history list stored in file.
    • H_SAVE, const char *file — Save the history list to file.
    • H_SAVE_FP, FILE *fp — Save the history list to the opened FILE pointer fp.
    • H_NSAVE_FP, size_t n, FILE *fp — Save the last n history entries to the opened FILE pointer fp.
    • H_SETUNIQUE, int unique — Set flag that adjacent identical event strings should not be entered into the history.
    • H_GETUNIQUE — Retrieve the current setting if adjacent identical elements should be entered into the history.
    • H_DEL, int e — Delete the event numbered e. This function is only provided for readline compatibility. The caller is responsible for free'ing the string in the returned HistEvent. Yes, caller, that means you, bestie — cleanup is your era.

history() returns >= 0 if the operation op succeeds. Otherwise, -1 is returned and ev is updated to contain more details about the error.

🧚 TOKENIZATION FUNCTIONS 🧚

The tokenization functions use a common data structure, Tokenizer, which is created by tok_init() and freed by tok_end(). Tokenizer bestie has entered the chat.

The following functions are available:

  • tok_init() — Initialize the tokenizer, and return a data structure to be used by all other tokenizer functions. IFS contains the Input Field Separators, which defaults to space, tab, and newline if NULL.
  • tok_end() — Clean up and finish with t, assumed to have been created with tok_init().
  • tok_reset() — Reset the tokenizer state. Use after a line has been successfully tokenized by tok_line() or tok_str() and before a new line is to be tokenized.
  • tok_line() — Tokenize li. If successful, modify:
    • argv to contain the words,
    • argc to contain the number of words,
    • cursorc (if not NULL) to contain the index of the word containing the cursor, and
    • cursoro (if not NULL) to contain the offset within argv[cursorc] of the cursor.

Returns 0 if successful, -1 for an internal error, 1 for an unmatched single quote, 2 for an unmatched double quote, and 3 for a backslash-quoted newline. A positive exit code indicates that another line should be read and tokenization attempted again. So if you get a positive code, don't spiral — read another line and try again.

  • tok_str() — A simpler form of tok_line(); str is a NUL terminated string to tokenize.

👀 SEE ALSO 👀

sh(1), signal(3), termcap(3), editrc(5), termcap(5), editline(7) — the whole little friend group.

🌈 HISTORY 🌈

The editline library first appeared in Bx 4.4. CC_REDISPLAY appeared in Nx 1.3. CC_REFRESH_BEEP, EL_EDITMODE, and the readline emulation appeared in Nx 1.4. EL_RPROMPT appeared in Nx 1.5. Timeline lore, preserved exactly.

👑 AUTHORS 👑

Heads up: the original starts this section with the little roff bit -nosplit. Then the credit roll is:

  • Christos Zoulas — the editline library was written by Christos Zoulas.
  • Luke Mewburn — wrote this manual and implemented CC_REDISPLAY, CC_REFRESH_BEEP, EL_EDITMODE, and EL_RPROMPT.
  • Jaromir Dolecek — implemented the readline emulation.
  • Johny Mattsson — implemented wide-character support.

💀 BUGS 💀

⚠️ Caveat, bestie: At this time, it is the responsibility of the caller to check the result of the EL_EDITMODE operation of el_get() (after an el_source() or el_parse()) to determine if editline should be used for further input. I.e., EL_EDITMODE is purely an indication of the result of the most recent editrc(5) edit command.

Original footer source/version and date: EDITLINE(3) • August 15, 2021 — that's the whole page, bestie. Mwah 💋✨

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