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DIRNAME(1P) POSIX Programmer's Manual DIRNAME(1P)
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.
dirname — return the directory portion of a pathname
dirname string
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
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.
None.
The following operand shall be supported:
string A string.
Not used.
None.
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 POSIX.1‐2008, Section 8.2, Internationalization
Variables 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.
Default.
The dirname utility shall write a line to the standard output in the
following format:
"%s\n", <resulting string>
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
Default.
The following sections are informative.
The definition of 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.
┌─────────────────┬─────────────┐
│ 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.
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 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
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.1‐2008, Section
3.267, Pathname allows trailing <slash> characters. The basename and
dirname utilities have to specify consistent handling for all valid
pathnames.
None.
Section 2.5, Parameters and Variables, basename(1p)
The Base Definitions volume of POSIX.1‐2008, Section 3.267, Pathname,
Chapter 8, Environment Variables
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 .
IEEE/The Open Group 2013 DIRNAME(1P)
Pages that refer to this page: basename(1p)