.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "BASENAME" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" basename 
.SH NAME
basename \- return non-directory portion of a pathname
.SH SYNOPSIS
.LP
\fBbasename\fP \fIstring\fP \fB[\fP\fIsuffix\fP\fB]\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 filename corresponding to the
last pathname component in \fIstring\fP and then the suffix
string \fIsuffix\fP, if present, shall be removed. This shall be done
by performing actions equivalent to the following steps in
order:
.IP " 1." 4
If \fIstring\fP is a null string, it is unspecified whether the resulting
string is \fB'.'\fP or a null string. In either
case, skip steps 2 through 6.
.LP
.IP " 2." 4
If \fIstring\fP is \fB"//"\fP , it is implementation-defined whether
steps 3 to 6 are skipped or processed.
.LP
.IP " 3." 4
If \fIstring\fP consists entirely of slash characters, \fIstring\fP
shall be set to a single slash character. In this case,
skip steps 4 to 6.
.LP
.IP " 4." 4
If there are any trailing slash characters in \fIstring\fP, they shall
be removed.
.LP
.IP " 5." 4
If there are any slash characters remaining in \fIstring\fP, the prefix
of \fIstring\fP up to and including the last slash
character in \fIstring\fP shall be removed.
.LP
.IP " 6." 4
If the \fIsuffix\fP operand is present, is not identical to the characters
remaining in \fIstring\fP, and is identical to a
suffix of the characters remaining in \fIstring\fP, the suffix \fIsuffix\fP
shall be removed from \fIstring\fP. Otherwise,
\fIstring\fP is not modified by this step. It shall not be considered
an error if \fIsuffix\fP is not found in \fIstring\fP.
.LP
.LP
The resulting string shall be written to standard output.
.SH OPTIONS
.LP
None.
.SH OPERANDS
.LP
The following operands shall be supported:
.TP 7
\fIstring\fP
A string.
.TP 7
\fIsuffix\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
\fIbasename\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 \fIbasename\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
.LP
If the string \fIstring\fP is a valid pathname:
.sp
.RS
.nf

\fB$(basename "\fP\fIstring\fP\fB")
\fP
.fi
.RE
.LP
produces a filename that could be used to open the file named by \fIstring\fP
in the directory returned by:
.sp
.RS
.nf

\fB$(dirname "\fP\fIstring\fP\fB")
\fP
.fi
.RE
.LP
If the string \fIstring\fP is not a valid pathname, the same algorithm
is used, but the result need not be a valid filename.
The \fIbasename\fP utility is not expected to make any judgements
about the validity of \fIstring\fP as a pathname; it just
follows the specified algorithm to produce a result string.
.LP
The following shell script compiles \fB/usr/src/cmd/cat.c\fP and moves
the output to a file named \fBcat\fP in the current
directory when invoked with the argument \fB/usr/src/cmd/cat\fP or
with the argument \fB/usr/src/cmd/cat.c\fP:
.sp
.RS
.nf

\fBc99 $(dirname "$1")/$(basename "$1" .c).c
mv a.out $(basename "$1" .c)
\fP
.fi
.RE
.SH RATIONALE
.LP
The behaviors of \fIbasename\fP and \fIdirname\fP 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 early proposal versions of these utilities
due to the way it specified handling of trailing
slashes.
.LP
Since the definition of \fIpathname\fP specifies implementation-defined
behavior for pathnames starting with two slash
characters, this volume of IEEE\ Std\ 1003.1-2001 specifies similar
implementation-defined behavior for the \fIbasename\fP
and \fIdirname\fP utilities.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIParameters and Variables\fP , \fIdirname\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 .