DIRNAME(1P) POSIX Programmer's Manual DIRNAME(1P)
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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.
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 POSIX.1-2008, Section 3.267, Pathname. The
string string shall be converted to the name of the directory contain-
ing the filename corresponding to the last pathname component in
string, performing actions equivalent to the following steps in order:
1. If string is //, skip steps 2 to 5.
2. If string consists entirely of <slash> characters, string shall be
set to a single <slash> character. In this case, skip steps 3 to 8.
3. If there are any trailing <slash> characters in string, they shall
be removed.
4. 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.
5. If there are any trailing non-<slash> characters in string, they
shall be removed.
6. If the remaining string is //, it is implementation-defined whether
steps 7 and 8 are skipped or processed.
7. If there are any trailing <slash> characters in string, they shall
be removed.
8. If the remaining string is empty, string shall be set to a single
<slash> character.
The resulting string shall be written to standard output.
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 internationalization vari-
ables that are unset or null. (See the Base Definitions vol-
ume of POSIX.1-2008, Section 8.2, Internationalization Vari-
ables for the precedence of internationalization variables
used to determine the values of locale categories.)
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 messages 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, applica-
tions 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.
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 |
+-----------------+-------------+
See also the examples for the basename utility.
RATIONALE
The dirname utility originated in System III. It has evolved through
the System V releases to a version that matches the requirements speci-
fied 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 POSIX.1-2008
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 pro-
posals 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.1-2008, Section 3.267, Pathname allows
trailing <slash> characters. The basename and dirname utilities have to
specify consistent handling for all valid pathnames.
FUTURE DIRECTIONS
None.
SEE ALSO
Section 2.5, Parameters and Variables, basename
The Base Definitions volume of POSIX.1-2008, Section 3.267, Pathname,
Chapter 8, Environment Variables
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 Electri-
cal 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.ker-
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 DIRNAME(1P)
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