DIRNAME(3P)                                         POSIX Programmer's Manual                                        DIRNAME(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       dirname - report the parent directory name of a file pathname

SYNOPSIS
       #include <libgen.h>

       char *dirname(char *path);


DESCRIPTION
       The  dirname()  function  shall  take a pointer to a character string that contains a pathname, and return a pointer to a
       string that is a pathname of the parent directory of that file. Trailing '/' characters in the path are  not  counted  as
       part of the path.

       If  path  does  not contain a '/', then dirname() shall return a pointer to the string "." . If path is a null pointer or
       points to an empty string, dirname() shall return a pointer to the string "."  .

       The dirname() function need not be reentrant. A function that is not required to be  reentrant  is  not  required  to  be
       thread-safe.

RETURN VALUE
       The dirname() function shall return a pointer to a string that is the parent directory of path. If path is a null pointer
       or points to an empty string, a pointer to a string "." is returned.

       The dirname() function may modify the string pointed to by path, and may return a pointer to static storage that may then
       be overwritten by subsequent calls to dirname().

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
       The  following  code  fragment reads a pathname, changes the current working directory to the parent directory, and opens
       the file.


              char path[PATH_MAX], *pathcopy;
              int fd;
              fgets(path, PATH_MAX, stdin);
              pathcopy = strdup(path);
              chdir(dirname(pathcopy));
              fd = open(basename(path), O_RDONLY);

   Sample Input and Output Strings for dirname()
       In the following table, the input string is the value pointed to by path, and the output string is the  return  value  of
       the dirname() function.

                                                     Input String   Output String
                                                     "/usr/lib"     "/usr"
                                                     "/usr/"        "/"
                                                     "usr"          "."
                                                     "/"            "/"
                                                     "."            "."
                                                     ".."           "."

   Changing the Current Directory to the Parent Directory
       The following program fragment reads a pathname, changes the current working directory to the parent directory, and opens
       the file.


              #include <unistd.h>
              #include <limits.h>
              #include <stdio.h>
              #include <fcntl.h>
              #include <string.h>
              #include <libgen.h>
              ...
              char path[PATH_MAX], *pathcopy;
              int fd;
              ...
              fgets(path, PATH_MAX, stdin);
              pathcopy = strdup(path);
              chdir(dirname(pathcopy));
              fd = open(basename(path), O_RDONLY);

APPLICATION USAGE
       The dirname() and basename() functions together yield a complete pathname. The expression dirname(path) obtains the path-
       name of the directory where basename(path) is found.

       Since  the  meaning  of  the  leading "//" is implementation-defined, dirname(" //foo) may return either "//" or '/' (but
       nothing else).

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       basename(), the Base Definitions volume of IEEE Std 1003.1-2001, <libgen.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any
       discrepancy  between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group
       Standard  is  the  referee   document.   The   original   Standard   can   be   obtained   online   at   http://www.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                   DIRNAME(3P)