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)):
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.
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 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 array we_wordv
contains the words found, followed by a NULL.
The flag
argument is a bitwise inclusive OR of the following values:
Append the words found to the array resulting from a previous call.
Insert we_offs
initial NULLs in the array we_wordv
. (These are not counted in the returned we_wordc
.)
Don't do command substitution.
The argument p
resulted from a previous call to wordexp(), and wordfree() was not called. Reuse the allocated storage.
Normally during command substitution stderr
is redirected to /dev/null
. This flag specifies that stderr
is not to be redirected.
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.
Illegal occurrence of newline or one of |, &, ;, <, >, (, ), {, }.
An undefined shell variable was referenced, and the WRDE_UNDEF flag told us to consider this an error.
Command substitution requested, but the WRDE_NOCMD flag told us to consider this an error.
Out of memory.
Shell syntax error, such as unbalanced parentheses or unmatched quotes.
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;
wordexp("[a-c]*.c", &p, 0);
w = p.we_wordv;
for (int i = 0; i < p.we_wordc; i++)
printf("%s\n", w[i]);
wordfree(&p);
exit(EXIT_SUCCESS);
}
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.
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