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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | VERSIONS | ATTRIBUTES | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON |
WORDEXP(3) Linux Programmer's Manual WORDEXP(3)
wordexp, wordfree - perform word expansion like a posix-shell
#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
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.
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 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.
wordexp() and wordfree() are provided in glibc since version 2.1.
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. wordexp() calls those functions, so we use race:utent to
remind users.
POSIX.1-2001, POSIX.1-2008.
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);
}
fnmatch(3), glob(3)
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2016-10-08 WORDEXP(3)
Pages that refer to this page: fnmatch(3), glob(3)