wordexp(3)
NAME
wordexp, wordfree - perform word expansion like a posix-shell
SYNOPSIS
#include <wordexp.h> int wordexp(const char *s, wordexp_t *p, int flags); void wordfree(wordexp_t *p); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): wordexp(), wordfree(): _XOPEN_SOURCE
DESCRIPTION
The function wordexp() performs a shell-like expansion of the string s
and returns the result in the structure pointed to by p. The data type
wordexp_t is a structure that at least has the fields we_wordc,
we_wordv, and we_offs. The field we_wordc is a size_t that gives the
number of words in the expansion of s. The field we_wordv is a char **
that points to the array of words found. The field we_offs of type
size_t is sometimes (depending on flags, see below) used to indicate
the number of initial elements in the we_wordv array that should be
filled with NULLs.
- The function wordfree() frees the allocated memory again. More precisely, it does not free its argument, but it frees the array we_wordv
and the strings that points to.
- The string argument
- Since the expansion is the same as the expansion by the shell (see sh(1)) of the parameters to a command, the string s must not contain characters that would be illegal in shell command parameters. In particular, there must not be any unescaped newline or |, &, ;, <, >, (, ), {, } characters outside a command substitution or parameter substitution context.
- If the argument s contains a word that starts with an unquoted comment character #, then it is unspecified whether that word and all following words are ignored, or the # is treated as a non-comment character.
- The expansion
- The expansion done consists of the following stages: tilde expansion (replacing ~user by user's home directory), variable substitution (replacing $FOO by the value of the environment variable FOO), command substitution (replacing $(command) or `command` by the output of command), arithmetic expansion, field splitting, wildcard expansion, quote removal.
- The result of expansion of special parameters ($@, $*, $#, $?, $-, $$, $!, $0) is unspecified.
- Field splitting is done using the environment variable $IFS. If it is not set, the field separators are space, tab and newline.
- The output array
- The array we_wordv contains the words found, followed by a NULL.
- The flags argument
- The flag argument is a bitwise inclusive OR of the following values:
- WRDE_APPEND
Append the words found to the array resulting from a previous call.
- WRDE_DOOFFS
Insert we_offs initial NULLs in the array we_wordv. (These are not counted in the returned we_wordc.)
- WRDE_NOCMD
Don't do command substitution.
- WRDE_REUSE
The argument p resulted from a previous call to wordexp(), and wordfree() was not called. Reuse the allocated storage.
- WRDE_SHOWERR
Normally during command substitution stderr is redirected to /dev/null. This flag specifies that stderr is not to be redirected.
- WRDE_UNDEF
Consider it an error if an undefined shell variable is expanded.
RETURN VALUE
In case of success 0 is returned. In case of error one of the following five values is returned.
- WRDE_BADCHAR
- Illegal occurrence of newline or one of |, &, ;, <, >, (, ), {, }.
- WRDE_BADVAL
- An undefined shell variable was referenced, and the WRDE_UNDEF flag told us to consider this an error.
- WRDE_CMDSUB
- Command substitution occurred, and the WRDE_NOCMD flag told us to consider this an error.
- WRDE_NOSPACE
- Out of memory.
- WRDE_SYNTAX
- Shell syntax error, such as unbalanced parentheses or unmatched quotes.
VERSIONS
wordexp() and wordfree() are provided in glibc since version 2.1.
CONFORMING TO
POSIX.1-2001.
EXAMPLE
The output of the following example program is approximately that of
"ls [a-c]*.c".
#include <stdio.h>
#include <stdlib.h>
#include <wordexp.h>
- int
main(int argc, char **argv)
{ - wordexp_t p;
char **w;
int i; - wordexp("[a-c]*.c", &p, 0);
w = p.we_wordv;
for (i = 0; i < p.we_wordc; i++)printf("%s\n", w[i]); - wordfree(&p);
exit(EXIT_SUCCESS); - }
SEE ALSO
COLOPHON
- This page is part of release 3.25 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.