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 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
 | Thread safety | MT-Unsafe race:utent const:env env sig:ALRM timer locale
 | 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
fnmatch(3), glob(3)