wordexp - Man Page
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 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
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. wordexp() 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
Referenced By
dunst(5), fnmatch(3), glob(3), icewm(1), icewm-env(5), kanshi(5), sudo.conf(5), sudoers(5), sway(5).
The man page wordfree(3) is an alias of wordexp(3).