GLOB(3) Library Functions Manual GLOB(3)

glob globfree — generate pathnames matching a pattern

#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);

The glob () function is a pathname generator that shall implement the rules defined in XCU Pattern Matching Notation, with optional support for rule 3 in XCU Patterns Used for Filename Expansion.

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

Member Type Member Name Description
size_t gl_pathc Count of paths matched by pattern.
char ** gl_pathv Pointer to a list of matched pathnames.
size_t gl_offs Slots to reserve at the beginning of gl_pathv.

The argument pattern is a pointer to a pathname pattern to be expanded. The glob () function shall match all accessible pathnames against this pattern and develop a list of all pathnames that match. In order to have access to a pathname, 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: ‘*’, ‘’?, and [‘’.

The glob () function shall store the number of matched pathnames into pglob -> gl_pathc and a pointer to a list of pointers to pathnames into pglob -> gl_pathv. The pathnames shall be in sort order as defined by the current setting of the LC_COLLATE category; see XBD V1_chap07(7). The first pointer after the last pathname shall be a null pointer. If the pattern does not match any pathnames, the returned number of matched paths is set to 0, and the contents of pglob -> gl_pathv are implementation-defined.

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

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 <glob.h>:

Append pathnames generated to the ones from a previous call to glob ().
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 shall point to pglob -> gl_offs null pointers, followed by pglob -> gl_pathc pathname pointers, followed by a null pointer.
Cause glob () to return when it encounters a directory that it cannot open or read. Ordinarily, glob () continues to find matches.
Each pathname that is a directory that matches pattern shall have a <slash> appended.
Supports rule 3 in XCU . If pattern does not match any pathname, then glob () shall return a list consisting of only pattern , and the number of matched pathnames is 1.
Disable backslash escaping.
Ordinarily, glob () sorts the matching pathnames according to the current setting of the LC_COLLATE category; see XBD LC_COLLATE . When this flag is used, the order of pathnames returned is unspecified.

The GLOB_APPEND flag can be used to append a new set of pathnames to those found in a previous call to glob (). The following rules apply to applications 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 shall not set GLOB_APPEND. All subsequent calls shall set it.
  2. All the calls shall set GLOB_DOOFFS, or all shall 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 -> .
    2. Pointers to the pathnames that were in the pglob -> gl_pathv list before the call, in the same order as before.
    3. Pointers to the new pathnames generated by the second call, in the specified order.
  4. The count returned in pglob -> gl_pathc shall be the total number of pathnames from the two calls.
  5. The application can change any of the fields after a call to glob (). If it does, the application shall reset them to the original value before a subsequent call, using the same pglob value, to globfree () or glob () with the GLOB_APPEND flag.

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

If ( *errfunc ()) is called and returns non-zero, or if the GLOB_ERR flag is set in flags, glob () shall stop the scan and return 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 shall be ignored.

The glob () function shall not fail because of large files.

Upon successful completion, glob () shall return 0. The argument pglob -> gl_pathc shall return the number of matched pathnames and the argument pglob -> gl_pathv shall contain a pointer to a null-terminated list of matched and sorted pathnames. However, if pglob -> gl_pathc is 0, the content of pglob -> gl_pathv is undefined.

The globfree () function shall not return a value.

If glob () terminates due to an error, it shall return one of the non-zero constants defined in <glob.h>. The arguments pglob -> gl_pathc and pglob -> gl_pathv are still set as defined above.

The glob () function shall fail and return the corresponding value if:

The scan was stopped because GLOB_ERR was set or ( *errfunc ()) returned non-zero.
The pattern does not match any existing pathname, and GLOB_NOCHECK was not set in flags.
An attempt to allocate memory failed.

One use of the GLOB_DOOFFS flag is by applications that build an argument list for use with execv(3), execve(3), or execvp(3). 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);
...

This function is not provided for the purpose of enabling utilities to perform pathname 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 pathname 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 pathname matches a given pattern, it can use fnmatch(3).

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 pathname if wildcards are specified, but wants to treat the pattern as just a string otherwise. The sh(1) utility might use this for option-arguments, for example.

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

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

It was claimed that the GLOB_DOOFFS flag is unnecessary because it could be simulated using:

new = (char **)malloc((n + pglob->gl_pathc + 1)
       * sizeof(char *));
(void) memcpy(new+n, pglob->gl_pathv,
       pglob->gl_pathc * sizeof(char *));
(void) memset(new, 0, n * sizeof(char *));
free(pglob->gl_pathv);
pglob->gl_pathv = new;

However, this assumes that the memory pointed to by gl_pathv is a block that was separately created using malloc(3). This is not necessarily the case. An application should make no assumptions about how the memory referenced by fields in pglob was allocated. It might have been obtained from malloc(3) in a large chunk and then carved up within glob (), or it might have been created using a different memory allocator. It is not the intent of the standard developers to specify or imply how the memory used by glob () is managed.

The GLOB_APPEND flag would be used when an application wants to expand several different patterns into a single list.

None.

exec(3), fdopendir(3), fnmatch(3), fstatat(3), readdir(3), wordexp(3)

XBD V1_chap07(7), <glob.h>

First released in Issue 4. Derived from the ISO POSIX-2 standard.

Moved from POSIX2 C-language Binding to BASE.

The normative text is updated to avoid use of the term "must" for application requirements.

The keyword is added to the glob () prototype for alignment with the ISO/IEC 9899:1999 (“ISO C99”) standard.

January 1, 2013 posix.fail