wordexp(3)

NAME

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

SYNOPSIS

   #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

   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

   In case of success 0  is  returned.   In  case  of  error  one  of  the
   following five values is returned.

   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.

VERSIONS

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

ATTRIBUTES

   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.

CONFORMING TO

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

EXAMPLE

   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(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]);
       wordfree(&p);
       exit(EXIT_SUCCESS);
   }

SEE ALSO

   fnmatch(3), glob(3)

COLOPHON

   This page is part of release 4.09 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
   https://www.kernel.org/doc/man-pages/.

                              2016-10-08                        WORDEXP(3)

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