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CD(P)			   POSIX Programmer's Manual			 CD(P)

NAME
       cd - change the working directory

SYNOPSIS
       cd [-L | -P] [directory]

       cd -


DESCRIPTION
       The  cd utility shall change the working directory of the current shell
       execution environment (see Shell Execution Environment )	 by  executing
       the  following  steps  in sequence. (In the following steps, the symbol
       curpath represents an intermediate value used to simplify the  descrip‐
       tion  of the algorithm used by cd. There is no requirement that curpath
       be made visible to the application.)

	1. If no directory operand is given and the HOME environment  variable
	   is  empty  or  undefined,  the  default behavior is implementation-
	   defined and no further steps shall be taken.

	2. If no directory operand is given and the HOME environment  variable
	   is  set to a non-empty value, the cd utility shall behave as if the
	   directory named in the HOME environment variable was	 specified  as
	   the directory operand.

	3. If the directory operand begins with a slash character, set curpath
	   to the operand and proceed to step 7.

	4. If the first component of the directory operand is dot or  dot-dot,
	   proceed to step 6.

	5. Starting  with  the first pathname in the colon-separated pathnames
	   of CDPATH (see the ENVIRONMENT VARIABLES section) if	 the  pathname
	   is  non-null,  test	if the concatenation of that pathname, a slash
	   character, and the directory operand	 names	a  directory.  If  the
	   pathname is null, test if the concatenation of dot, a slash charac‐
	   ter, and the operand names a directory.  In	either	case,  if  the
	   resulting  string  names an existing directory, set curpath to that
	   string and proceed to step 7.  Otherwise, repeat this step with the
	   next pathname in CDPATH until all pathnames have been tested.

	6. Set	curpath to the string formed by the concatenation of the value
	   of PWD , a slash character, and the operand.

	7. If the -P option is in effect, the cd utility shall perform actions
	   equivalent to the chdir() function, called with curpath as the path
	   argument. If these actions succeed, the  PWD	 environment  variable
	   shall be set to an absolute pathname for the current working direc‐
	   tory and shall not contain filename components that, in the context
	   of  pathname	 resolution, refer to a file of type symbolic link. If
	   there is insufficient permission on the new directory,  or  on  any
	   parent  of  that directory, to determine the current working direc‐
	   tory, the value of the PWD environment variable is unspecified.  If
	   the actions equivalent to chdir() fail for any reason, the cd util‐
	   ity shall display an appropriate error message and  not  alter  the
	   PWD environment variable. Whether the actions equivalent to chdir()
	   succeed or fail, no further steps shall be taken.

	8. The curpath value shall then be converted to canonical form as fol‐
	   lows,   considering	each  component	 from  beginning  to  end,  in
	   sequence:

	    a. Dot components and any slashes that separate them from the next
	       component shall be deleted.

	    b. For  each  dot-dot component, if there is a preceding component
	       and it is neither root nor dot-dot,  the	 preceding  component,
	       all  slashes  separating	 the preceding component from dot-dot,
	       dot-dot and all slashes separating dot-dot from	the  following
	       component shall be deleted.

	    c. An  implementation may further simplify curpath by removing any
	       trailing slash characters that are not  also  leading  slashes,
	       replacing  multiple non-leading consecutive slashes with a sin‐
	       gle slash, and replacing three or more leading slashes  with  a
	       single  slash.  If,  as	a result of this canonicalization, the
	       curpath variable is null, no further steps shall be taken.

	9. The cd utility shall then perform actions equivalent to the chdir()
	   function called with curpath as the path argument. If these actions
	   failed for any reason, the cd utility shall display an  appropriate
	   error  message  and no further steps shall be taken.	 The PWD envi‐
	   ronment variable shall be set to curpath.

       If, during the execution of the above steps, the PWD environment	 vari‐
       able  is changed, the OLDPWD environment variable shall also be changed
       to the value of the old working directory (that is the current  working
       directory immediately prior to the call to cd).

OPTIONS
       The  cd	utility	 shall	conform	 to  the  Base	Definitions  volume of
       IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported by the implementation:

       -L     Handle the operand dot-dot logically; symbolic  link  components
	      shall  not  be  resolved before dot-dot components are processed
	      (see steps 8. and 9. in the DESCRIPTION).

       -P     Handle the operand dot-dot physically; symbolic link  components
	      shall  be	 resolved before dot-dot components are processed (see
	      step 7. in the DESCRIPTION).

       If both -L and -P options are specified,	 the  last  of	these  options
       shall  be  used	and all others ignored. If neither -L nor -P is speci‐
       fied, the operand shall be handled dot-dot logically; see the  DESCRIP‐
       TION.

OPERANDS
       The following operands shall be supported:

       directory
	      An  absolute  or	relative  pathname of the directory that shall
	      become the new working directory. The interpretation of a	 rela‐
	      tive  pathname by cd depends on the -L option and the CDPATH and
	      PWD environment variables. If directory is an empty string,  the
	      results are unspecified.

       -      When  a  hyphen is used as the operand, this shall be equivalent
	      to the command:

	      cd "$OLDPWD" && pwd

       which changes to the previous working directory	and  then  writes  its
       name.

STDIN
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of cd:

       CDPATH A	 colon-separated  list of pathnames that refer to directories.
	      The cd utility shall use this list in its attempt to change  the
	      directory,  as  described in the DESCRIPTION. An empty string in
	      place of a directory pathname represents the current  directory.
	      If CDPATH is not set, it shall be treated as if it were an empty
	      string.

       HOME   The name of the directory, used when  no	directory  operand  is
	      specified.

       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 .

       OLDPWD A pathname of the previous working directory, used by cd -.

       PWD    This variable shall be set as specified in the  DESCRIPTION.  If
	      an application sets or unsets the value of PWD , the behavior of
	      cd is unspecified.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       If a non-empty directory name from CDPATH is used, or if cd - is	 used,
       an  absolute  pathname of the new working directory shall be written to
       the standard output as follows:

	      "%s\n", <new directory>

       Otherwise, there shall be no output.

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     The directory was successfully changed.

       >0     An error occurred.

CONSEQUENCES OF ERRORS
       The working directory shall remain unchanged.

       The following sections are informative.

APPLICATION USAGE
       Since cd affects the current shell execution environment, it is	always
       provided	 as a shell regular built-in. If it is called in a subshell or
       separate utility execution environment, such as one of the following:

	      (cd /tmp)
	      nohup cd
	      find . -exec cd {} \;

       it does not affect the working directory of the caller's environment.

       The user must have execute (search) permission in directory in order to
       change to it.

EXAMPLES
       None.

RATIONALE
       The use of the CDPATH was introduced in the System V shell.  Its use is
       analogous to the use of the PATH variable in the shell. The BSD C shell
       used a shell parameter cdpath for this purpose.

       A common extension when HOME is undefined is to get the login directory
       from the user database for the invoking user.  This does not  occur  on
       System V implementations.

       Some  historical	 shells,  such	as the KornShell, took special actions
       when the directory name contained a dot-dot  component,	selecting  the
       logical	parent	of the directory, rather than the actual parent direc‐
       tory; that is, it moved up one level toward the '/'  in	the  pathname,
       remembering  what the user typed, rather than performing the equivalent
       of:

	      chdir("..");

       In such a shell, the following commands would not  necessarily  produce
       equivalent output for all directories:

	      cd .. && ls      ls ..

       This behavior is now the default. It is not consistent with the defini‐
       tion of dot-dot in most historical practice; that is, while this behav‐
       ior  has	 been optionally available in the KornShell, other shells have
       historically not supported this functionality. The logical pathname  is
       stored  in  the	PWD environment variable when the cd utility completes
       and this value is used to construct the next directory name  if	cd  is
       invoked with the -L option.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Shell  Execution	 Environment  ,	 pwd , the System Interfaces volume of
       IEEE Std 1003.1-2001, chdir()

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				 CD(P)
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