WORDEXP(3)                  Linux Programmer's Manual                 WORDEXP(3)

       wordexp, wordfree - perform word expansion like a posix-shell

       #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():

       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:

              Append the words found to the array resulting from a previous

              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

              Consider it an error if an undefined shell variable is expanded.

       On success, wordexp() returns 0.  On failure, wordexp() returns one of
       the following nonzero values:

              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

       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

       #include <stdio.h>
       #include <stdlib.h>
       #include <wordexp.h>

       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]);

       fnmatch(3), glob(3)

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       latest version of this page, can be found at

                                   2021-08-27                         WORDEXP(3)