DIRNAME(P) POSIX Programmer's Manual DIRNAME(P)NAMEdirname - return the directory portion of a pathname
SYNOPSISdirname 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, Path‐
name. 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:
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 variables
that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, 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 slashes to the beginning of a pathname
unless they can ensure that there are more or less than two or are pre‐
pared 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 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
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 pro‐
posals 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 basename and dirname utilities have to specify consistent
handling for all valid pathnames.
FUTURE DIRECTIONS
None.
SEE ALSObasename() , 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 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 .
IEEE/The Open Group 2003 DIRNAME(P)
