basename(3) — Linux manual page


BASENAME(3)               Linux Programmer's Manual              BASENAME(3)

NAME         top

       basename, dirname - parse pathname components

SYNOPSIS         top

       #include <libgen.h>

       char *dirname(char *path);

       char *basename(char *path);

DESCRIPTION         top

       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

       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         top

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

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface             Attribute     Value   │
       │basename(), dirname() │ Thread safety │ MT-Safe │

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008.

NOTES         top

       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         top

       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.

EXAMPLES         top

       The following code snippet demonstrates the use of basename() and
           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         top

       basename(1), dirname(1)

COLOPHON         top

       This page is part of release 5.09 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

GNU                              2020-06-09                      BASENAME(3)

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