mirror of https://github.com/mkerrisk/man-pages
137 lines
3.8 KiB
Plaintext
137 lines
3.8 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "DIRNAME" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" dirname
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.SH NAME
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dirname \- report the parent directory name of a file pathname
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.SH SYNOPSIS
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.LP
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\fB#include <libgen.h>
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.br
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.sp
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char *dirname(char *\fP\fIpath\fP\fB); \fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIdirname\fP() function shall take a pointer to a character string
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that contains a pathname, and return a pointer to a
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string that is a pathname of the parent directory of that file. Trailing
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\fB'/'\fP characters in the path are not counted as
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part of the path.
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.LP
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If \fIpath\fP does not contain a \fB'/'\fP , then \fIdirname\fP()
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shall return a pointer to the string \fB"."\fP . If
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\fIpath\fP is a null pointer or points to an empty string, \fIdirname\fP()
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shall return a pointer to the string \fB"."\fP
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\&.
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.LP
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The \fIdirname\fP() function need not be reentrant. A function that
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is not required to be reentrant is not required to be
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thread-safe.
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.SH RETURN VALUE
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.LP
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The \fIdirname\fP() function shall return a pointer to a string that
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is the parent directory of \fIpath\fP. If \fIpath\fP is
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a null pointer or points to an empty string, a pointer to a string
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\fB"."\fP is returned.
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.LP
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The \fIdirname\fP() function may modify the string pointed to by \fIpath\fP,
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and may return a pointer to static storage that
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may then be overwritten by subsequent calls to \fIdirname\fP().
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.SH ERRORS
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.LP
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No errors are defined.
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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The following code fragment reads a pathname, changes the current
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working directory to the parent directory, and opens the
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file.
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.sp
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.RS
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.nf
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\fBchar path[PATH_MAX], *pathcopy;
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int fd;
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fgets(path, PATH_MAX, stdin);
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pathcopy = strdup(path);
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chdir(dirname(pathcopy));
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fd = open(basename(path), O_RDONLY);
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\fP
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.fi
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.RE
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.SS Sample Input and Output Strings for dirname()
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.LP
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In the following table, the input string is the value pointed to by
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\fIpath\fP, and the output string is the return value of
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the \fIdirname\fP() function.
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.TS C
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center; l l.
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\fBInput String\fP \fBOutput String\fP
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"/usr/lib" "/usr"
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"/usr/" "/"
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"usr" "."
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"/" "/"
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"." "."
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".." "."
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.TE
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.SS Changing the Current Directory to the Parent Directory
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.LP
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The following program fragment reads a pathname, changes the current
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working directory to the parent directory, and opens the
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file.
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.sp
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.RS
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.nf
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\fB#include <unistd.h>
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#include <limits.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <string.h>
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#include <libgen.h>
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\&...
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char path[PATH_MAX], *pathcopy;
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int fd;
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\&...
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fgets(path, PATH_MAX, stdin);
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pathcopy = strdup(path);
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chdir(dirname(pathcopy));
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fd = open(basename(path), O_RDONLY);
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\fP
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.fi
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.RE
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.SH APPLICATION USAGE
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.LP
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The \fIdirname\fP() and \fIbasename\fP() functions together yield
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a complete
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pathname. The expression \fIdirname\fP(\fIpath\fP) obtains the pathname
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of the directory where \fIbasename\fP(\fIpath\fP) is
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found.
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.LP
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Since the meaning of the leading \fB"//"\fP is implementation-defined,
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\fIdirname\fP(" \fB//foo\fP) may return either
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\fB"//"\fP or \fB'/'\fP (but nothing else).
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIbasename\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
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\fI<libgen.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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