glob

, globfree

- generate path names matching a pattern

Synopsis

#include <glob.h>

int glob(const char *restrict pattern, int flags,
     int(*errfunc)(const char *epath, int eerrno),
     glob_t *restrict pglob);

void globfree(glob_t *pglob);

Description

The glob() function is a path name generator.

The globfree() function frees any memory allocated by glob() associated with pglob.

pattern Argument

The argument pattern is a pointer to a path name pattern to be expanded. The glob() function matches all accessible path names against this pattern and develops a list of all path names that match. In order to have access to a path name, glob() requires search permission on every component of a path except the last, and read permission on each directory of any filename component of pattern that contains any of the following special characters:

*        ?        [

pglob Argument

The structure type glob_t is defined in the header <glob.h> and includes at least the following members:

size_t   gl_pathc;     /* count of paths matched by */
                       /* pattern */
char     **gl_pathv;   /* pointer to list of matched */
                       /* path names */
size_t   gl_offs;      /* slots to reserve at beginning */
                       /* of gl_pathv */

The glob() function stores the number of matched path names into pglob->gl_pathc and a pointer to a list of pointers to path names into pglob->gl_pathv. The path names are in sort order as defined by the current setting of the LC_COLLATE category. The first pointer after the last path name is a NULL pointer. If the pattern does not match any path names, the returned number of matched paths is set to 0, and the contents of pglob->gl_pathv are implementation-dependent.

It is the caller's responsibility to create the structure pointed to by pglob. The glob() function allocates other space as needed, including the memory pointed to by gl_pathv. The globfree() function frees any space associated with pglob from a previous call to glob().

flags Argument

The flags argument is used to control the behavior of glob(). The value of flags is a bitwise inclusive OR of zero or more of the following constants, which are defined in the header <glob.h>:

GLOB_APPEND

Append path names generated to the ones from a previous call to glob().

GLOB_DOOFFS

Make use of pglob->gl_offs. If this flag is set, pglob->gl_offs is used to specify how many NULL pointers to add to the beginning of pglob->gl_pathv. In other words, pglob->gl_pathv will point to pglob->gl_offs NULL pointers, followed by pglob->gl_pathc path name pointers, followed by a NULL pointer.

GLOB_ERR

Causes glob() to return when it encounters a directory that it cannot open or read. Ordinarily, glob() continues to find matches.

GLOB_LIMIT

Limit the total number of returned pathnames to the value of 65536. This also limits the total number of stat and readdir(3C) calls to prevent high CPU usage.

GLOB_MARK

Each path name that is a directory that matches pattern has a slash appended.

GLOB_NOCHECK

If pattern does not match any path name, then glob() returns a list consisting of only pattern, and the number of matched path names is 1.

GLOB_NOESCAPE

Disable backslash escaping.

GLOB_NOSORT

Ordinarily, glob() sorts the matching path names according to the current setting of the LC_COLLATE category. When this flag is used the order of path names returned is unspecified.

The GLOB_APPEND flag can be used to append a new set of path names to those found in a previous call to glob(). The following rules apply when two or more calls to glob() are made with the same value of pglob and without intervening calls to globfree():

1. The first such call must not set GLOB_APPEND. All subsequent calls must set it.

2. All the calls must set GLOB_DOOFFS, or all must not set it.

3. After the second call, pglob->gl_pathv points to a list containing the following:

   1. Zero or more NULL pointers, as specified by GLOB_DOOFFS and pglob->gl_offs.

   2. Pointers to the path names that were in the pglob->gl_pathv list before the call, in the same order as before.

   3. Pointers to the new path names generated by the second call, in the specified order.

4. The count returned in pglob->gl_pathc will be the total number of path names from the two calls.

5. The application can change any of the fields after a call to glob(). If it does, it must reset them to the original value before a subsequent call, using the same pglob value, to globfree() or glob() with the GLOB_APPEND flag.

errfunc and epath Arguments

If, during the search, a directory is encountered that cannot be opened or read and errfunc is not a NULL pointer, glob() calls (*errfunc) with two arguments:

1. The epath argument is a pointer to the path that failed.

2. The eerrno argument is the value of errno from the failure, as set by the opendir(3C), readdir(3C) or stat(2) functions. (Other values may be used to report other errors not explicitly documented for those functions.)

The following constants are defined as error return values for glob():

GLOB_ABORTED

The scan was stopped because GLOB_ERR was set or (*errfunc) returned non-zero.

GLOB_NOMATCH

The pattern does not match any existing path name, and GLOB_NOCHECK was not set in flags.

GLOG_NOSPACE

An attempt to allocate memory failed.

If (*errfunc) is called and returns non-zero, or if the GLOB_ERR flag is set in flags, glob() stops the scan and returns GLOB_ABORTED after setting gl_pathc and gl_pathv in pglob to reflect the paths already scanned. If GLOB_ERR is not set and either errfunc is a NULL pointer or (*errfunc) returns 0, the error is ignored.

Return Values

The following values are returned by glob():

0

Successful completion. The argument pglob->gl_pathc returns the number of matched path names and the argument pglob->gl_pathv contains a pointer to a null-terminated list of matched and sorted path names. However, if pglob->gl_pathc is 0, the content of pglob->gl_pathv is undefined.

non-zero

An error has occurred. Non-zero constants are defined in <glob.h>. The arguments pglob->gl_pathc and pglob->gl_pathv are still set as defined above.

The globfree() function returns no value.

Usage

This function is not provided for the purpose of enabling utilities to perform path name expansion on their arguments, as this operation is performed by the shell, and utilities are explicitly not expected to redo this. Instead, it is provided for applications that need to do path name expansion on strings obtained from other sources, such as a pattern typed by a user or read from a file.

If a utility needs to see if a path name matches a given pattern, it can use fnmatch(3C).

Note that gl_pathc and gl_pathv have meaning even if glob() fails. This allows glob() to report partial results in the event of an error. However, if gl_pathc is 0, gl_pathv is unspecified even if glob() did not return an error.

The GLOB_NOCHECK option could be used when an application wants to expand a path name if wildcards are specified, but wants to treat the pattern as just a string otherwise.

The new path names generated by a subsequent call with GLOB_APPEND are not sorted together with the previous path names. This mirrors the way that the shell handles path name expansion when multiple expansions are done on a command line.

Applications that need tilde and parameter expansion should use the wordexp(3C) function.

Examples

Example 1 Example of glob_doofs function.

One use of the GLOB_DOOFFS flag is by applications that build an argument list for use with the execv(), execve(), or execvp() functions (see exec(2)). Suppose, for example, that an application wants to do the equivalent of:

ls -l *.c

but for some reason:

system("ls -l *.c")

is not acceptable. The application could obtain approximately the same result using the sequence:

globbuf.gl_offs = 2;
glob ("*.c", GLOB_DOOFFS, NULL, &globbuf);
globbuf.gl_pathv[0] = "ls";
globbuf.gl_pathv[1] = "-l";
execvp ("ls", &globbuf.gl_pathv[0]);

Using the same example:

ls -l *.c *.h

could be approximately simulated using GLOB_APPEND as follows:

globbuf.gl_offs = 2;
glob ("*.c", GLOB_DOOFFS, NULL, &globbuf);
glob ("*.h", GLOB_DOOFFS|GLOB_APPEND, NULL, &globbuf);
. . .

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

execv(2), stat(2), fnmatch(3C), opendir(3C), readdir(3C), wordexp(3C), attributes(5), standards(5)