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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | VERSIONS | STANDARDS | HISTORY | BUGS | EXAMPLES | SEE ALSO | COLOPHON |
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basename(3) Library Functions Manual basename(3)
basename, dirname - parse pathname components
Standard C library (libc, -lc)
#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 │
└──────────────────────────────────────┴───────────────┴─────────┘
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.
POSIX.1-2008.
POSIX.1-2001.
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)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
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Linux man-pages 6.15 2025-05-17 basename(3)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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