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.TH DIRNAME "1P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH 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.

.SH NAME

dirname

\(em return the directory portion of a pathname

.SH SYNOPSIS

.LP

.nf

dirname \fIstring\fR

.fi

.SH DESCRIPTION

The

.IR string

operand shall be treated as a pathname, as defined in the Base Definitions volume of POSIX.1\(hy2008,

.IR "Section 3.267" ", " "Pathname".

The string

.IR string

shall be converted to the name of the directory containing the

filename corresponding to the last pathname component in

.IR string ,

performing actions equivalent to the following steps in order:

.IP " 1." 4

If

.IR string

is

.BR // ,

skip steps 2 to 5.

.IP " 2." 4

If

.IR string

consists entirely of

<slash>

characters,

.IR string

shall be set to a single

<slash>

character. In this case, skip steps 3 to 8.

.IP " 3." 4

If there are any trailing

<slash>

characters in

.IR string ,

they shall be removed.

.IP " 4." 4

If there are no

<slash>

characters remaining in

.IR string ,

.IR string

shall be set to a single

<period>

character. In this case, skip steps 5 to 8.

.IP " 5." 4

If there are any trailing non-\c

<slash>

characters in

.IR string ,

they shall be removed.

.IP " 6." 4

If the remaining

.IR string

is

.BR // ,

it is implementation-defined whether steps 7 and 8 are skipped or

processed.

.IP " 7." 4

If there are any trailing

<slash>

characters in

.IR string ,

they shall be removed.

.IP " 8." 4

If the remaining

.IR string

is empty,

.IR string

shall be set to a single

<slash>

character.

.P

The resulting string shall be written to standard output.

.SH OPTIONS

None.

.SH OPERANDS

The following operand shall be supported:

.IP "\fIstring\fR" 10

A string.

.SH STDIN

Not used.

.SH "INPUT FILES"

None.

.SH "ENVIRONMENT VARIABLES"

The following environment variables shall affect the execution of

.IR dirname :

.IP "\fILANG\fP" 10

Provide a default value for the internationalization variables that are

unset or null. (See the Base Definitions volume of POSIX.1\(hy2008,

.IR "Section 8.2" ", " "Internationalization Variables"

for the precedence of internationalization variables used to determine

the values of locale categories.)

.IP "\fILC_ALL\fP" 10

If set to a non-empty string value, override the values of all the

other internationalization variables.

.IP "\fILC_CTYPE\fP" 10

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).

.IP "\fILC_MESSAGES\fP" 10

.br

Determine the locale that should be used to affect the format and

contents of diagnostic messages written to standard error.

.IP "\fINLSPATH\fP" 10

Determine the location of message catalogs for the processing of

.IR LC_MESSAGES .

.SH "ASYNCHRONOUS EVENTS"

Default.

.SH STDOUT

The

.IR dirname

utility shall write a line to the standard output in the following

format:

.sp

.RS 4

.nf

\fB

"%s\en", <\fIresulting string\fR>

.fi \fR

.P

.RE

.SH STDERR

The standard error shall be used only for diagnostic messages.

.SH "OUTPUT FILES"

None.

.SH "EXTENDED DESCRIPTION"

None.

.SH "EXIT STATUS"

The following exit values shall be returned:

.IP "\00" 6

Successful completion.

.IP >0 6

An error occurred.

.SH "CONSEQUENCES OF ERRORS"

Default.

.LP

.IR "The following sections are informative."

.SH "APPLICATION USAGE"

The definition of

.IR pathname

specifies implementation-defined behavior for pathnames starting with

two

<slash>

characters. Therefore, applications shall not arbitrarily add

<slash>

characters 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

center tab(@) box;

cB | cB

l | l.

Command@Results

_

\fIdirname\fR /@/

\fIdirname\fR //@/ or //

\fIdirname\fR /\fIa\fR/\fIb\fR/@/\fIa\fR

\fIdirname\fR //\fIa\fR//\fIb\fR//@//\fIa\fR

\fIdirname\fR@Unspecified

\fIdirname a\fR@. ($? = 0)

\fIdirname\fR ""@. ($? = 0)

\fIdirname\fR /\fIa\fR@/

\fIdirname\fR /\fIa\fR/\fIb\fR@/\fIa\fR

\fIdirname\fR \fIa\fR/\fIb\fR@\fIa\fR

.TE

.P

See also the examples for the

.IR basename

utility.

.SH RATIONALE

The

.IR dirname

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

.IR dirname .

.P

The behaviors of

.IR basename

and

.IR dirname

in this volume of POSIX.1\(hy2008 have been coordinated so that when

.IR string

is a valid pathname:

.sp

.RS 4

.nf

\fB

$(basename -- "\fIstring\fP")

.fi \fR

.P

.RE

.P

would be a valid filename for the file in the directory:

.sp

.RS 4

.nf

\fB

$(dirname -- "\fIstring\fP")

.fi \fR

.P

.RE

.P

This would not work for the versions of these utilities in early proposals

due to the way processing of trailing

<slash>

characters was specified. Consideration was given to leaving processing

unspecified if there were trailing

<slash>

characters, but this cannot be done; the Base Definitions volume of POSIX.1\(hy2008,

.IR "Section 3.267" ", " "Pathname"

allows trailing

<slash>

characters. The

.IR basename

and

.IR dirname

utilities have to specify consistent handling for all valid pathnames.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "Section 2.5" ", " "Parameters and Variables",

.IR "\fIbasename\fR\^"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "Section 3.267" ", " "Pathname",

.IR "Chapter 8" ", " "Environment Variables"

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 7, Copyright (C) 2013 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group.

(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .