.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "DIRNAME" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" dirname 
.SH NAME
dirname \- return the directory portion of a pathname
.SH SYNOPSIS
.LP
\fBdirname\fP \fIstring\fP
.SH DESCRIPTION
.LP
The \fIstring\fP operand shall be treated as a pathname, as defined
in the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 3.266, Pathname. The string
\fIstring\fP shall be converted to the name of the directory containing
the filename corresponding to the last pathname component
in \fIstring\fP, performing actions equivalent to the following steps
in order:
.IP " 1." 4
If \fIstring\fP is \fB//\fP, skip steps 2 to 5.
.LP
.IP " 2." 4
If \fIstring\fP consists entirely of slash characters, \fIstring\fP
shall be set to a single slash character. In this case,
skip steps 3 to 8.
.LP
.IP " 3." 4
If there are any trailing slash characters in \fIstring\fP, they shall
be removed.
.LP
.IP " 4." 4
If there are no slash characters remaining in \fIstring\fP, \fIstring\fP
shall be set to a single period character. In this
case, skip steps 5 to 8.
.LP
.IP " 5." 4
If there are any trailing non-slash characters in \fIstring\fP, they
shall be removed.
.LP
.IP " 6." 4
If the remaining \fIstring\fP is \fB//\fP, it is implementation-defined
whether steps 7 and 8 are skipped or processed.
.LP
.IP " 7." 4
If there are any trailing slash characters in \fIstring\fP, they shall
be removed.
.LP
.IP " 8." 4
If the remaining \fIstring\fP is empty, \fIstring\fP shall be set
to a single slash character.
.LP
.LP
The resulting string shall be written to standard output.
.SH OPTIONS
.LP
None.
.SH OPERANDS
.LP
The following operand shall be supported:
.TP 7
\fIstring\fP
A string.
.sp
.SH STDIN
.LP
Not used.
.SH INPUT FILES
.LP
None.
.SH ENVIRONMENT VARIABLES
.LP
The following environment variables shall affect the execution of
\fIdirname\fP:
.TP 7
\fILANG\fP
Provide a default value for the internationalization variables that
are unset or null. (See the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables
for
the precedence of internationalization variables used to determine
the values of locale categories.)
.TP 7
\fILC_ALL\fP
If set to a non-empty string value, override the values of all the
other internationalization variables.
.TP 7
\fILC_CTYPE\fP
Determine the locale for the interpretation of sequences of bytes
of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments).
.TP 7
\fILC_MESSAGES\fP
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard
error.
.TP 7
\fINLSPATH\fP
Determine the location of message catalogs for the processing of \fILC_MESSAGES
\&.\fP 
.sp
.SH ASYNCHRONOUS EVENTS
.LP
Default.
.SH STDOUT
.LP
The \fIdirname\fP utility shall write a line to the standard output
in the following format:
.sp
.RS
.nf

\fB"%s\\n", <\fP\fIresulting string\fP\fB>
\fP
.fi
.RE
.SH STDERR
.LP
The standard error shall be used only for diagnostic messages.
.SH OUTPUT FILES
.LP
None.
.SH EXTENDED DESCRIPTION
.LP
None.
.SH EXIT STATUS
.LP
The following exit values shall be returned:
.TP 7
\ 0
Successful completion.
.TP 7
>0
An error occurred.
.sp
.SH CONSEQUENCES OF ERRORS
.LP
Default.
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
The definition of \fIpathname\fP specifies implementation-defined
behavior for pathnames starting with two slash characters.
Therefore, applications shall not arbitrarily add slashes to the beginning
of a pathname unless they can ensure that there are more
or less than two or are prepared to deal with the implementation-defined
consequences.
.SH EXAMPLES
.TS C
center; l l.
\fBCommand\fP	\fBResults\fP
\fIdirname\fP /	/
\fIdirname\fP //	/ or //
\fIdirname\fP /\fIa\fP/\fIb\fP/	/\fIa\fP
\fIdirname\fP //\fIa\fP//\fIb\fP//	//\fIa\fP
\fIdirname\fP	Unspecified
\fIdirname a\fP	. ($? = 0)
\fIdirname\fP ""	. ($? = 0)
\fIdirname\fP /\fIa\fP	/
\fIdirname\fP /\fIa\fP/\fIb\fP	/\fIa\fP
\fIdirname\fP \fIa\fP/\fIb\fP	\fIa\fP
.TE
.SH RATIONALE
.LP
The \fIdirname\fP utility originated in System III. It has evolved
through the System V releases to a version that matches the
requirements specified in this description in System V Release 3.
4.3 BSD and earlier versions did not include \fIdirname\fP.
.LP
The behaviors of \fIbasename\fP and \fIdirname\fP in this volume of
IEEE\ Std\ 1003.1-2001 have been coordinated so that when \fIstring\fP
is a valid pathname:
.sp
.RS
.nf

\fB$(basename "\fP\fIstring\fP\fB")
\fP
.fi
.RE
.LP
would be a valid filename for the file in the directory:
.sp
.RS
.nf

\fB$(dirname "\fP\fIstring\fP\fB")
\fP
.fi
.RE
.LP
This would not work for the versions of these utilities in early proposals
due to the way processing of trailing slashes was
specified. Consideration was given to leaving processing unspecified
if there were trailing slashes, but this cannot be done; the
Base Definitions volume of IEEE\ Std\ 1003.1-2001, Section 3.266,
Pathname allows trailing slashes. The \fIbasename\fP and \fIdirname\fP
utilities
have to specify consistent handling for all valid pathnames.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIbasename\fP() , \fIParameters and Variables\fP
.SH 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, 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 .