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WORDEXP(3)            DragonFly Library Functions Manual            WORDEXP(3)


NAME

     wordexp - perform shell-style word expansions


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <wordexp.h>

     int
     wordexp(const char * restrict words, wordexp_t * restrict we, int flags);

     void
     wordfree(wordexp_t *we);


DESCRIPTION

     The wordexp() function performs shell-style word expansion on words and
     places the list of words into the we_wordv member of we, and the number
     of words into we_wordc.

     The flags argument is the bitwise inclusive OR of any of the following
     constants:

     WRDE_APPEND       Append the words to those generated by a previous call
                       to wordexp().

     WRDE_DOOFFS       As many NULL pointers as are specified by the we_offs
                       member of we are added to the front of we_wordv.

     WRDE_NOCMD        Disallow command substitution in words.  See the note
                       in BUGS before using this.

     WRDE_REUSE        The we argument was passed to a previous successful
                       call to wordexp() but has not been passed to
                       wordfree().  The implementation may reuse the space
                       allocated to it.

     WRDE_SHOWERR      Do not redirect shell error messages to /dev/null.

     WRDE_UNDEF        Report error on an attempt to expand an undefined shell
                       variable.

     The wordexp_t structure is defined in <wordexp.h> as:

           typedef struct {
                   size_t  we_wordc;       /* count of words matched */
                   char    **we_wordv;     /* pointer to list of words */
                   size_t  we_offs;        /* slots to reserve in we_wordv */
           } wordexp_t;

     The wordfree() function frees the memory allocated by wordexp().


IMPLEMENTATION NOTES

     The wordexp() function is implemented using the undocumented wordexp2
     shell built-in command.


RETURN VALUES

     The wordexp() function returns zero if successful, otherwise it returns
     one of the following error codes:

     WRDE_BADCHAR      The words argument contains one of the following
                       unquoted characters: <newline>, `|', `&', `;', `<',
                       `>', `(', `)', `{', `}'.

     WRDE_BADVAL       An error after successful parsing, such as an attempt
                       to expand an undefined shell variable with WRDE_UNDEF
                       set in flags.

     WRDE_CMDSUB       An attempt was made to use command substitution and
                       WRDE_NOCMD is set in flags.

     WRDE_NOSPACE      Not enough memory to store the result or an error
                       during fork(2).

     WRDE_SYNTAX       Shell syntax error in words.

     The wordfree() function returns no value.


ENVIRONMENT

     IFS      Field separator.


EXAMPLES

     Invoke the editor on all .c files in the current directory and /etc/motd
     (error checking omitted):

           wordexp_t we;

           wordexp("${EDITOR:-vi} *.c /etc/motd", &we, 0);
           execvp(we.we_wordv[0], we.we_wordv);


DIAGNOSTICS

     Diagnostic messages from the shell are written to the standard error
     output if WRDE_SHOWERR is set in flags.


SEE ALSO

     sh(1), fnmatch(3), glob(3), popen(3), system(3)


STANDARDS

     The wordexp() and wordfree() functions conform to IEEE Std 1003.1-2001
     ("POSIX.1").


BUGS

     The current wordexp() implementation does not recognize multibyte
     characters other than UTF-8, since the shell (which it invokes to perform
     expansions) does not.


SECURITY CONSIDERATIONS

     Pathname generation may create output that is exponentially larger than
     the input size.

     Although this implementation detects command substitution reliably for
     WRDE_NOCMD, the attack surface remains fairly large.  Also, some other
     implementations (such as older versions of this one) may execute command
     substitutions even if WRDE_NOCMD is set.

DragonFly 5.9-DEVELOPMENT       October 9, 2020      DragonFly 5.9-DEVELOPMENT

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