DIRNAME
Section: POSIX Programmer's Manual (3P)
Updated: 2017
Page Index
PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
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. The
dirname()
function shall not perform pathname resolution; the result shall not be
affected by whether or not
path
exists or by its file type. Trailing
'/'
characters in the path that are not also leading
'/'
characters shall not be 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 may modify the string pointed to by
path,
and may return a pointer to static storage that may then be
overwritten by a subsequent call to
dirname().
The
dirname()
function need not be thread-safe.
RETURN VALUE
The
dirname()
function shall return a pointer to a string as described above.
The
dirname()
function may modify the string pointed to by
path,
and may return a pointer to internal storage. The returned pointer
might be invalidated or the storage might be overwritten by a
subsequent call to
dirname().
The returned pointer might also be invalidated if the calling
thread is terminated.
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 = NULL, *pathcopy;
size_t buflen = 0;
ssize_t linelen = 0;
int fd;
linelen = getline(&path, &buflen, stdin);
path[linelen-1] = 0;
pathcopy = strdup(path);
if (chdir(dirname(pathcopy)) < 0) {
...
}
if ((fd = open(basename(path), O_RDONLY)) >= 0) {
...
close (fd);
}
...
free (pathcopy);
free (path);
The EXAMPLES section of the
basename()
function (see
basename())
includes a table showing examples of the results of processing
several sample pathnames by the
basename()
and
dirname()
functions and by the
basename
and
dirname
utilities.
APPLICATION USAGE
The
dirname()
and
basename()
functions together yield a complete pathname. The expression
dirname(
path) obtains the pathname 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 POSIX.1-2017,
<libgen.h>
The Shell and Utilities volume of POSIX.1-2017,
basename,
dirname
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .