Linux man page for dirname.3

dirname(3) -- Linux man page

NAME

dirname, basename - 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 copies should be passed to these functions. Furthermore, dirname and basename may return pointers to statically allocated memory which may be overwritten by subsequent calls.

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"
"/"             "/"             "/"
"."             "."             "."
".."            "."             ".."

EXAMPLE

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);

RETURN VALUE

Both dirname and basename return pointers to null-terminated strings.

NOTES

There are two different versions of basename - the POSIX version described above, and the GNU version one gets after

  #define _GNU_SOURCE


  #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 of the POSIX versions of these functions they modify their argument, and segfault when called with a static string like "/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.

CONFORMING TO

POSIX 1003.1-2001