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 freebsd_wordexp 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.

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.