wordexp(3) — Linux manual page


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

NAME         top

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

SYNOPSIS         top

       #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)):

       wordexp(), wordfree(): _XOPEN_SOURCE

DESCRIPTION         top

       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

   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

RETURN VALUE         top

       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.

VERSIONS         top

       wordexp() and wordfree() are provided in glibc since version 2.1.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │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.

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008.

EXAMPLES         top

       The output of the following example program is approximately that of
       "ls [a-c]*.c".

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

       main(int argc, char **argv)
           wordexp_t p;
           char **w;
           int i;

           wordexp("[a-c]*.c", &p, 0);
           w = p.we_wordv;
           for (i = 0; i < p.we_wordc; i++)
               printf("%s\n", w[i]);

SEE ALSO         top

       fnmatch(3), glob(3)

COLOPHON         top

       This page is part of release 5.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

                                 2020-06-09                       WORDEXP(3)

Pages that refer to this page: fnmatch(3)glob(3)globfree(3)