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Linux 2.6 - man page for dirname (linux section 3)

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

       basename, dirname - parse pathname components

       #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 direc-
       tory 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 base-
       name() 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 overwrit-
       ten 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).)


       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

       With  glibc, one gets the POSIX version of basename() when <libgen.h> is included, and the
       GNU version otherwise.

       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 '/'  char-
       acters, and generated a segfault if given a NULL argument.

	   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 release 3.55 of the Linux man-pages project.  A description of the
       project,    and	  information	 about	  reporting    bugs,	can    be    found     at

GNU					    2009-03-30				      BASENAME(3)

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