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BASENAME(3) Linux Programmer's Manual BASENAME(3)
NAME
basename, dirname - parse pathname components
SYNOPSIS
#include <libgen.h>
char *dirname(char *path);
char *basename(char *path);
DESCRIPTION
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
/ / /
. . .
.. . ..
RETURN VALUE
Both dirname() and basename() return pointers to null-terminated strings. (Do not pass these pointers to free(3).)
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼───────────────┼─────────┤
│basename(), dirname() │ Thread safety │ MT-Safe │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
NOTES
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.
BUGS
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 ar‐
gument.
EXAMPLES
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);
SEE ALSO
basename(1), dirname(1)
GNU 2021-03-22 BASENAME(3)