[MAN] glob

Content-type: text/html; charset=UTF-8

GLOB

Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
Index Return to Main Contents

---

 

NAME

glob, globfree - find pathnames matching a pattern, free memory from glob()  

SYNOPSIS

#include <glob.h>

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

 

DESCRIPTION

The glob() function searches for all the pathnames matching pattern according to the rules used by the shell (see glob(7)). No tilde expansion or parameter substitution is done; if you want these, use wordexp(3).

The globfree() function frees the dynamically allocated storage from an earlier call to glob().

The results of a glob() call are stored in the structure pointed to by pglob. This structure is of type glob_t (declared in <glob.h>) and includes the following elements defined by POSIX.2 (more may be present as an extension):

typedef struct {
    size_t   gl_pathc;    /* Count of paths matched so far  */
    char   **gl_pathv;    /* List of matched pathnames.  */
    size_t   gl_offs;     /* Slots to reserve in gl_pathv.  */ } glob_t;

Results are stored in dynamically allocated storage.

The argument flags is made up of the bitwise OR of zero or more the following symbolic constants, which modify the behavior of glob():

GLOB_ERR

Return upon a read error (because a directory does not have read permission, for example). By default, glob() attempts carry on despite errors, reading all of the directories that it can.

GLOB_MARK

Append a slash to each path which corresponds to a directory.

GLOB_NOSORT

Don't sort the returned pathnames. The only reason to do this is to save processing time. By default, the returned pathnames are sorted.

GLOB_DOOFFS

Reserve pglob->gl_offs slots at the beginning of the list of strings in pglob->pathv. The reserved slots contain null pointers.

GLOB_NOCHECK

If no pattern matches, return the original pattern. By default, glob() returns GLOB_NOMATCH if there are no matches.

GLOB_APPEND

Append the results of this call to the vector of results returned by a previous call to glob(). Do not set this flag on the first invocation of glob().

GLOB_NOESCAPE

Don't allow backslash ('\') to be used as an escape character. Normally, a backslash can be used to quote the following character, providing a mechanism to turn off the special meaning metacharacters.

flags may also include any of the following, which are GNU extensions and not defined by POSIX.2:

GLOB_PERIOD

Allow a leading period to be matched by metacharacters. By default, metacharacters can't match a leading period.

GLOB_ALTDIRFUNC

Use alternative functions pglob->gl_closedir, pglob->gl_readdir, pglob->gl_opendir, pglob->gl_lstat, and pglob->gl_stat for filesystem access instead of the normal library functions.

GLOB_BRACE

Expand csh(1) style brace expressions of the form {a,b}. Brace expressions can be nested. Thus, for example, specifying the pattern "{foo/{,cat,dog},bar}" would return the same results as four separate glob() calls using the strings: "foo/", "foo/cat", "foo/dog", and "bar".

GLOB_NOMAGIC

If the pattern contains no metacharacters, then it should be returned as the sole matching word, even if there is no file with that name.

GLOB_TILDE

Carry out tilde expansion. If a tilde ('~') is the only character in the pattern, or an initial tilde is followed immediately by a slash ('/'), then the home directory of the caller is substituted for the tilde. If an initial tilde is followed by a username (e.g., "~andrea/bin"), then the tilde and username are substituted by the home directory of that user. If the username is invalid, or the home directory cannot be determined, then no substitution is performed.

GLOB_TILDE_CHECK

This provides behavior similar to that of GLOB_TILDE. The difference is that if the username is invalid, or the home directory cannot be determined, then instead of using the pattern itself as the name, glob() returns GLOB_NOMATCH to indicate an error.

GLOB_ONLYDIR

This is a hint to glob() that the caller is interested only in directories that match the pattern. If the implementation can easily determine file-type information, then nondirectory files are not returned to the caller. However, the caller must still check that returned files are directories. (The purpose of this flag is merely to optimize performance when the caller is interested only in directories.)

If errfunc is not NULL, it will be called in case of an error with the arguments epath, a pointer to the path which failed, and eerrno, the value of errno as returned from one of the calls to opendir(3), readdir(3), or stat(2). If errfunc returns nonzero, or if GLOB_ERR is set, glob() will terminate after the call to errfunc.

Upon successful return, pglob->gl_pathc contains the number of matched pathnames and pglob->gl_pathv contains a pointer to the list of pointers to matched pathnames. The list of pointers is terminated by a null pointer.

It is possible to call glob() several times. In that case, the GLOB_APPEND flag has to be set in flags on the second and later invocations.

As a GNU extension, pglob->gl_flags is set to the flags specified, ored with GLOB_MAGCHAR if any metacharacters were found.  

RETURN VALUE

On successful completion, glob() returns zero. Other possible returns are:

GLOB_NOSPACE

for running out of memory,

GLOB_ABORTED

for a read error, and

GLOB_NOMATCH

for no found matches.

 

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
glob()	Thread safety	MT-Unsafe race:utent env sig:ALRM timer locale
globfree()	Thread safety	MT-Safe

In the above table, utent in race:utent signifies that if any of the functions setutent(3), getutent(3), or endutent(3) are used in parallel in different threads of a program, then data races could occur. glob() calls those functions, so we use race:utent to remind users.  

CONFORMING TO

POSIX.1-2001, POSIX.1-2008, POSIX.2.  

NOTES

The structure elements gl_pathc and gl_offs are declared as size_t in glibc 2.1, as they should be according to POSIX.2, but are declared as int in glibc 2.0.  

BUGS

The glob() function may fail due to failure of underlying function calls, such as malloc(3) or opendir(3). These will store their error code in errno.  

EXAMPLE

One example of use is the following code, which simulates typing

ls -l *.c ../*.c

in the shell:

glob_t globbuf;

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

SEE ALSO

ls(1), sh(1), stat(2), exec(3), fnmatch(3), malloc(3), opendir(3), readdir(3), wordexp(3), glob(7)  

COLOPHON

This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

---

 

Index

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ATTRIBUTES

CONFORMING TO

NOTES

BUGS

EXAMPLE

SEE ALSO

COLOPHON

---

This document was created by man2html, using the manual pages.
Time: 04:45:43 GMT, September 16, 2022 Content-type: text/html; charset=UTF-8

GLOB

Section: Linux Programmer's Manual (7)
Updated: 2016-10-08
Index Return to Main Contents

---

 

NAME

glob - globbing pathnames  

DESCRIPTION

Long ago, in UNIX V6, there was a program /etc/glob that would expand wildcard patterns. Soon afterward this became a shell built-in.

These days there is also a library routine glob(3) that will perform this function for a user program.

The rules are as follows (POSIX.2, 3.13).  

Wildcard matching

A string is a wildcard pattern if it contains one of the characters '?', '*' or '['. Globbing is the operation that expands a wildcard pattern into the list of pathnames matching the pattern. Matching is defined by:

A '?' (not between brackets) matches any single character.

A '*' (not between brackets) matches any string, including the empty string.

Character classes

An expression "[...]" where the first character after the leading '[' is not an '!' matches a single character, namely any of the characters enclosed by the brackets. The string enclosed by the brackets cannot be empty; therefore ']' can be allowed between the brackets, provided that it is the first character. (Thus, "[][!]" matches the three characters '[', ']' and '!'.)

Ranges

There is one special convention: two characters separated by '-' denote a range. (Thus, "[A-Fa-f0-9]" is equivalent to "[ABCDEFabcdef0123456789]".) One may include '-' in its literal meaning by making it the first or last character between the brackets. (Thus, "[]-]" matches just the two characters ']' and '-', and "[--0]" matches the three characters '-', '.', '0', since '/' cannot be matched.)

Complementation

An expression "[!...]" matches a single character, namely any character that is not matched by the expression obtained by removing the first '!' from it. (Thus, "[!]a-]" matches any single character except ']', 'a' and '-'.)

One can remove the special meaning of '?', '*' and '[' by preceding them by a backslash, or, in case this is part of a shell command line, enclosing them in quotes. Between brackets these characters stand for themselves. Thus, "[[?*\]" matches the four characters '[', '?', '*' and '\'.  

Pathnames

Globbing is applied on each of the components of a pathname separately. A '/' in a pathname cannot be matched by a '?' or '*' wildcard, or by a range like "[.-0]". A range containing an explicit '/' character is syntactically incorrect. (POSIX requires that syntactically incorrect patterns are left unchanged.)

If a filename starts with a '.', this character must be matched explicitly. (Thus, rm * will not remove .profile, and tar c * will not archive all your files; tar c . is better.)  

Empty lists

The nice and simple rule given above: "expand a wildcard pattern into the list of matching pathnames" was the original UNIX definition. It allowed one to have patterns that expand into an empty list, as in

    xv -wait 0 *.gif *.jpg

where perhaps no *.gif files are present (and this is not an error). However, POSIX requires that a wildcard pattern is left unchanged when it is syntactically incorrect, or the list of matching pathnames is empty. With bash one can force the classical behavior using this command:

    shopt -s nullglob

(Similar problems occur elsewhere. For example, where old scripts have

    rm `find . -name "*~"`

new scripts require

    rm -f nosuchfile `find . -name "*~"`

to avoid error messages from rm called with an empty argument list.)  

NOTES

 

Regular expressions

Note that wildcard patterns are not regular expressions, although they are a bit similar. First of all, they match filenames, rather than text, and secondly, the conventions are not the same: for example, in a regular expression '*' means zero or more copies of the preceding thing.

Now that regular expressions have bracket expressions where the negation is indicated by a '^', POSIX has declared the effect of a wildcard pattern "[^...]" to be undefined.  

Character classes and internationalization

Of course ranges were originally meant to be ASCII ranges, so that "[ -%]" stands for "[ !"#$%]" and "[a-z]" stands for "any lowercase letter". Some UNIX implementations generalized this so that a range X-Y stands for the set of characters with code between the codes for X and for Y. However, this requires the user to know the character coding in use on the local system, and moreover, is not convenient if the collating sequence for the local alphabet differs from the ordering of the character codes. Therefore, POSIX extended the bracket notation greatly, both for wildcard patterns and for regular expressions. In the above we saw three types of items that can occur in a bracket expression: namely (i) the negation, (ii) explicit single characters, and (iii) ranges. POSIX specifies ranges in an internationally more useful way and adds three more types:

(iii) Ranges X-Y comprise all characters that fall between X and Y (inclusive) in the current collating sequence as defined by the LC_COLLATE category in the current locale.

(iv) Named character classes, like

[:alnum:]  [:alpha:]  [:blank:]  [:cntrl:]
[:digit:]  [:graph:]  [:lower:]  [:print:]
[:punct:]  [:space:]  [:upper:]  [:xdigit:]

so that one can say "[[:lower:]]" instead of "[a-z]", and have things work in Denmark, too, where there are three letters past 'z' in the alphabet. These character classes are defined by the LC_CTYPE category in the current locale.

(v) Collating symbols, like "[.ch.]" or "[.a-acute.]", where the string between "[." and ".]" is a collating element defined for the current locale. Note that this may be a multicharacter element.

(vi) Equivalence class expressions, like "[=a=]", where the string between "[=" and "=]" is any collating element from its equivalence class, as defined for the current locale. For example, "[[=a=]]" might be equivalent to "[aáàäâ]", that is, to "[a[.a-acute.][.a-grave.][.a-umlaut.][.a-circumflex.]]".  

SEE ALSO

sh(1), fnmatch(3), glob(3), locale(7), regex(7)  

COLOPHON

This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

---

 

Index

NAME

DESCRIPTION

Wildcard matching

Pathnames

Empty lists

NOTES

Regular expressions

Character classes and internationalization

SEE ALSO

COLOPHON

---

This document was created by man2html, using the manual pages.
Time: 04:45:58 GMT, September 16, 2022