wordexp(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | HISTORY | EXAMPLES | SEE ALSO | COLOPHON

wordexp(3)              Library Functions Manual              wordexp(3)

NAME         top

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

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #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         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 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         top

       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         top

       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         top

       POSIX.1-2008.

HISTORY         top

       POSIX.1-2001.  glibc 2.1.

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>

       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         top

       fnmatch(3), glob(3)

COLOPHON         top

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Linux man-pages 6.9.1          2024-06-15                     wordexp(3)

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