This manual page is part of the POSIX Programmers 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.
Sample Input and Output Strings for dirname()
Changing the Current Directory to the Parent Directory
dirname - report the parent directory name of a file pathname
char *dirname(char *path);
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.
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().
No errors are defined.
The following sections are informative.
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);
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" "." "/" "/" "." "." ".." "."
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);
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).
basename() , the Base Definitions volume of IEEE Std 1003.1-2001, <libgen.h>
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, Copyright (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.opengroup.org/unix/online.html .
|IEEE/The Open Group||DIRNAME (P)||2003|