basename, dirname — parse pathname components


#include <libgen.h>
char *dirname( char *path);
char *basename( char *path);


[Warning] Warning

There are two different functions basename() - see below.

The functions dirname() and basename() break a null-terminated pathname string into directory and filename components. In the usual case, dirname() returns the string up to, but not including, the final '/', and basename() returns the component following the final '/'. Trailing '/' characters are not counted as part of the pathname.

If path does not contain a slash, dirname() returns the string "." while basename() returns a copy of path. If path is the string "/", then both dirname() and basename() return the string "/". If path is a NULL pointer or points to an empty string, then both dirname() and basename() return the string ".".

Concatenating the string returned by dirname(), a "/", and the string returned by basename() yields a complete pathname.

Both dirname() and basename() may modify the contents of path, so it may be desirable to pass a copy when calling one of these functions.

These functions may return pointers to statically allocated memory which may be overwritten by subsequent calls. Alternatively, they may return a pointer to some part of path, so that the string referred to by path should not be modified or freed until the pointer returned by the function is no longer required.

The following list of examples (taken from SUSv2) shows the strings returned by dirname() and basename() for different paths:

path dirname basename
/usr/lib /usr lib
/usr/ / usr
usr . usr
/ / /
. . .
.. . ..


Both dirname() and basename() return pointers to null-terminated strings. (Do not pass these pointers to free(3).)




There are two different versions of basename() - the POSIX version described above, and the GNU version, which one gets after

    #define _GNU_SOURCE         /* See feature_test_macros(7) */
    #include <string.h>

The GNU version never modifies its argument, and returns the empty string when path has a trailing slash, and in particular also when it is "/". There is no GNU version of dirname().

With glibc, one gets the POSIX version of basename() when <libgen.h> is included, and the GNU version otherwise.


In the glibc implementation of the POSIX versions of these functions they modify their argument, and segfault when called with a static string like "/usr/". Before glibc 2.2.1, the glibc version of dirname() did not correctly handle pathnames with trailing '/' characters, and generated a segfault if given a NULL argument.


char *dirc, *basec, *bname, *dname;
char *path = "/etc/passwd";

dirc = strdup(path);
basec = strdup(path);
dname = dirname(dirc);
bname = basename(basec);
printf("dirname=%s, basename=%s\n", dname, bname);


basename(1), dirname(1)


This page is part of release 3.52 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at−pages/.

  Copyright (c) 2000 by Michael Kerrisk (

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.

Created, 14 Dec 2000 by Michael Kerrisk