wordexp(3) Library Functions Manual wordexp(3)
NAME
wordexp, wordfree - perform word expansion like a posix-shell
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <wordexp.h>
int wordexp(const char *restrict s, wordexp_t *restrict 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 pre-
cisely, 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 par-
ticular, 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 (re-
placing $FOO by the value of the environment variable FOO), command sub-
stitution (replacing $(command) or `command` by the output of command),
arithmetic expansion, field splitting, wildcard expansion, quote re-
moval.
The result of expansion of special parameters ($@, $*, $#, $?, $-, $$,
$!, $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 redi-
rected.
WRDE_UNDEF
Consider it an error if an undefined shell variable is expanded.
RETURN VALUE
On success, wordexp() returns 0. On failure, wordexp() returns one of
the following nonzero values:
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 requested, but 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.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌────────────┬───────────────┬─────────────────────────────────────────┐
│ Interface │ Attribute │ Value │
├────────────┼───────────────┼─────────────────────────────────────────┤
│ wordexp() │ Thread safety │ MT-Unsafe race:utent const:env env │
│ │ │ sig:ALRM timer locale │
├────────────┼───────────────┼─────────────────────────────────────────┤
│ wordfree() │ Thread safety │ MT-Safe │
└────────────┴───────────────┴─────────────────────────────────────────┘
In the above table, utent in race:utent signifies that if any of the
functions setutent(3), getutent(3), or endutent(3) are used in parallel
in different threads of a program, then data races could occur. word-
exp() calls those functions, so we use race:utent to remind users.
STANDARDS
POSIX.1-2008.
HISTORY
POSIX.1-2001. glibc 2.1.
EXAMPLES
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(void)
{
wordexp_t p;
char **w;
wordexp("[a-c]*.c", &p, 0);
w = p.we_wordv;
for (size_t i = 0; i < p.we_wordc; i++)
printf("%s\n", w[i]);
wordfree(&p);
exit(EXIT_SUCCESS);
}
SEE ALSO
fnmatch(3), glob(3)
Linux man-pages 6.9.1 2024-06-15 wordexp(3)
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