Name
wordexp, wordfree - perform word expansion like a posix-shellLibrary
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 byp. 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 \[ti]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 |
| T} | Thread safety | MT-Unsafe race:utent const:env env sig:ALRM timer locale |
| T} | 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\en", w[i]);
wordfree(&p);
exit(EXIT_SUCCESS);
}