NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES | BUGS | EXAMPLE | SEE ALSO | COLOPHON
BASENAME(3) Linux Programmer's Manual BASENAME(3)
basename, dirname - parse pathname components
#include <libgen.h>
char *dirname(char *path);
char *basename(char *path);
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).)
POSIX.1-2001.
There are two different versions of basename() - the POSIX version described
above, and the GNU version, which one gets after
#define _GNU_SOURCE
#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), feature_test_macros(7)
This page is part of release 3.23 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2009-03-30 BASENAME(3)