basename(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | BUGS | EXAMPLES | SEE ALSO | COLOPHON

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 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         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
       attributes(7).

       ┌──────────────────────────────────────┬───────────────┬─────────┐
       │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
       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         top

       basename(1), dirname(1)

COLOPHON         top

       This page is part of release 5.12 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
       https://www.kernel.org/doc/man-pages/.

GNU                            2021-03-22                    BASENAME(3)

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