Tribblix: manual page: glob.3c

GLOB(3C) Standard C Library Functions GLOB(3C)

NAME

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; /* Total count of paths matched by */
/* pattern */
char **gl_pathv; /* List of matched path names */
size_t gl_offs; /* # of slots reserved in gl_pathv */
int gl_matchc; /* Count of paths matching pattern. */
int gl_flags; /* Copy of flags parameter to glob. */

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_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.

GLOB_ALTDIRFUNC
The following additional fields in the pglob
structure have been initialized with alternate
functions for glob() to use to open, read, and close
directories and to get stat information on names
found in those directories:

void *(*gl_opendir)(const char *);
struct dirent *(*gl_readdir)(void *);
void (*gl_closedir)(void *);
int (*gl_lstat)(const char *, struct stat *);
int (*gl_stat)(const char *, struct stat *);

This extension is provided to allow programs such as
ufsrestore(8) to provide globbing from directories
stored on tape.

GLOB_BRACE
Pre-process the pattern string to expand
`{pat,pat,...}' strings like csh(1). The pattern
`{}' is left unexpanded for historical reasons.
(csh(1) does the same thing to ease typing of
find(1) patterns.)

GLOB_MAGCHAR
Set by the glob() function if the pattern included
globbing characters. See the description of the
usage of the gl_matchc structure member for more
details.

GLOB_NOMAGIC
Is the same as GLOB_NOCHECK but it only appends the
pattern if it does not contain any of the special
characters `*', `?', or `['. GLOB_NOMAGIC is
provided to simplify implementing the historic
csh(1) globbing behavior and should probably not be
used anywhere else.

GLOB_QUOTE
This option has no effect and is included for
backwards compatibility with older sources.

GLOB_TILDE
Expand patterns that start with `~' to user name
home directories.

GLOB_LIMIT
Limit the amount of memory used by matches to
ARG_MAX. This option should be set for programs
that can be coerced to a denial of service attack
via patterns that expand to a very large number of
matches, such as a long string of `*/../*/..'.

GLOB_KEEPSTAT
Retain a copy of the stat(2) information retrieved
for matching paths in the gl_statv array:

struct stat **gl_statv;

This option may be used to avoid lstat(2) lookups in
cases where they are expensive.

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:

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

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

c. 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.)

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

On successful completion, glob() returns zero. In addition the
fields of pglob contain the values described below:

gl_pathc
Contains the total number of matched pathnames so
far. This includes other matches from previous
invocations of glob() if GLOB_APPEND was specified.

gl_matchc
Contains the number of matched pathnames in the
current invocation of glob().

gl_flags
Contains a copy of the flags parameter with the bit
GLOB_MAGCHAR set if pattern contained any of the
special characters `*', `?', or `[', cleared if not.

gl_pathv
Contains a pointer to a null-terminated list of
matched pathnames. However, if gl_pathc is zero, the
contents of gl_pathv are undefined.

gl_statv
If the GLOB_KEEPSTAT flag was set, gl_statv contains
a pointer to a null-terminated list of matched
stat(2) objects corresponding to the paths in
gl_pathc.

If glob() terminates due to an error, it sets errno and returns one
of the following non-zero constants. defined in <glob.h>:

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.

GLOB_NOSPACE
An attempt to allocate memory failed.

GLOB_NOSYS
The requested function is not supported by this
version of glob().

The arguments pglob->gl_pathc and pglob->gl_pathv are still set as
specified 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