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Linux 2.6 - man page for dirname (linux section 1posix)

DIRNAME(P)			    POSIX Programmer's Manual			       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 vol-
       ume 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:

	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, Inter-
	      nationalization 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  interna-
	      tionalization 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  argu-
	      ments).

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic 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  start-
       ing  with two slash characters.	Therefore, applications 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 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 leaving process-
       ing unspecified if there were trailing slashes, but this cannot be done; the Base  Defini-
       tions 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  path-
       names.

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	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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				       DIRNAME(P)


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