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dirname(P) dirname(P)
NAME
dirname - return the directory portion of a pathname
SYNOPSIS
dirname string
DESCRIPTION
The string 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 string shall be converted to the name of the
directory containing the filename corresponding to the
last pathname component in string, performing actions
equivalent to the following steps in order:
If string is //, skip steps 2 to 5.
If string consists entirely of slash characters, string
shall be set to a single slash character. In this case,
skip steps 3 to 8.
If there are any trailing slash characters in string,
they shall be removed.
If there are no slash characters remaining in string,
string shall be set to a single period character. In
this case, skip steps 5 to 8.
If there are any trailing non-slash characters in
string, they shall be removed.
If the remaining string is //, it is implementation-
defined whether steps 7 and 8 are skipped or processed.
If there are any trailing slash characters in string,
they shall be removed.
If the remaining string is empty, string shall be set to
a single slash character.
The resulting string shall be written to standard out-
put.
OPTIONS
None.
OPERANDS
The following operand shall be supported:
string A string.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the
execution of dirname:
LANG Provide a default value for the internationaliza-
tion 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 cate-
gories.)
LC_ALL If set to a non-empty string value, override the
values of all the other internationalization
variables.
LC_CTYPE
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).
LC_MESSAGES
Determine the locale that should be used to
affect the format and contents of diagnostic mes-
sages written to standard error.
NLSPATH
Determine the location of message catalogs for
the processing of LC_MESSAGES .
ASYNCHRONOUS EVENTS
Default.
STDOUT
The dirname utility shall write a line to the standard
output in the following format:
"%s\n", <resulting string>
STDERR
The standard error shall be used only for diagnostic
messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
The definition of pathname specifies implementation-
defined behavior for pathnames starting with two slash
characters. Therefore, applications shall not arbitrar-
ily 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.
EXAMPLES
Command Results
dirname / /
dirname // / or //
dirname /a/b/ /a
dirname //a//b// //a
dirname Unspecified
dirname a . ($? = 0)
dirname "" . ($? = 0)
dirname /a /
dirname /a/b /a
dirname a/b a
RATIONALE
The 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 dirname.
The behaviors of basename and dirname in this volume of
IEEE Std 1003.1-2001 have been coordinated so that when
string is a valid pathname:
$(basename "string")
would be a valid filename for the file in the directory:
$(dirname "string")
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 leav-
ing 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 basename and dirname utili-
ties have to specify consistent handling for all valid
pathnames.
FUTURE DIRECTIONS
None.
SEE ALSO
basename() , Parameters and Variables
COPYRIGHT
Portions of this text are reprinted and reproduced in
electronic form from IEEE Std 1003.1, 2003 Edition,
Standard for Information Technology -- Portable Operat-
ing System Interface (POSIX), The Open Group Base Speci-
fications Issue 6, Copyright (C) 2001-2003 by the Insti-
tute 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.open-
group.org/unix/online.html .
POSIX 2003 dirname(P)
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