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).)
For an explanation of the terms used in this section, see
attributes(7).
| Interface |
Attribute |
Value |
| basename (), dirname () |
Thread safety |
MT-Safe |
POSIX.1-2001, POSIX.1-2008.
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, the POSIX versions of these functions modify the
path argument, and segfault when called with a static string such as
"/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.
The following code snippet demonstrates the use of
basename() and
dirname():
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)