segfault in pointer to string program Post: 302556104

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LEARN ABOUT SUSE

dirname

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

NAME

       basename, dirname - 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 '/'.  Trail-
       ing '/' 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

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

CONFORMING TO

       POSIX.1-2001.

NOTES

       There are two different versions of basename() - the POSIX version described above, and the GNU version, which 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.

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
", dname, bname);

SEE ALSO

       basename(1), dirname(1), feature_test_macros(7)

COLOPHON

       This page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU
								    2009-03-30							       BASENAME(3)