CD(1P)							     POSIX Programmer's Manual							    CD(1P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

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 Section 2.12,	Shell  Execution  Environ-
       ment)  by  executing  the following steps in sequence. (In the following steps, the symbol curpath represents an intermediate value used to
       simplify the description 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 if that pathname did not end with a <slash> character, and
	   the directory operand names a directory. If the pathname is null, test if the concatenation of dot, a <slash> character, and the  oper-
	   and	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 directory operand.

	7. If the -P option is in effect, proceed to step 10. If curpath does not begin with a <slash> character, set curpath to the string formed
	   by the concatenation of the value of PWD, a <slash> character if the value of PWD did not end with a <slash> character, and curpath.

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

	    a. Dot components and any <slash> characters 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, then:

		i.  If the preceding component does not refer (in the context of pathname resolution with symbolic links followed) to a directory,
		    then the cd utility shall display an appropriate error message and no further steps shall be taken.

	       ii.  The preceding component, all <slash> characters separating the preceding component from  dot-dot,  dot-dot,  and  all  <slash>
		    characters separating dot-dot from the following component (if any) shall be deleted.

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

	9. If curpath is longer than {PATH_MAX} bytes (including the terminating null) and the directory operand was not  longer  than	{PATH_MAX}
	   bytes (including the terminating null), then curpath shall be converted from an absolute pathname to an equivalent relative pathname if
	   possible. This conversion shall always be considered possible if the value of PWD, with a trailing <slash> added if it does not already
	   have  one,  is  an  initial	substring  of curpath.	Whether or not it is considered possible under other circumstances is unspecified.
	   Implementations may also apply this conversion if curpath is not longer than {PATH_MAX} bytes or the directory operand was longer  than
	   {PATH_MAX} bytes.

       10. The cd utility shall then perform actions equivalent to the chdir() function called with curpath as the path argument. If these actions
	   fail for any reason, the cd utility shall display an appropriate error message and the remainder of this step shall not be executed. If
	   the	-P  option  is	not  in  effect, the PWD environment variable shall be set to the value that curpath had on entry to step 9 (i.e.,
	   before conversion to a relative pathname). If the -P option is in effect, the PWD environment variable shall be set to the string  that
	   would  be output by pwd -P.	If there is insufficient permission on the new directory, or on any parent of that directory, to determine
	   the current working directory, the value of the PWD environment variable is unspecified.

       If, during the execution of the above steps, the PWD environment variable is set, the OLDPWD environment variable shall also be set 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 POSIX.1-2008, 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 specified,
       the operand shall be handled dot-dot logically; see the DESCRIPTION.

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  relative
		 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
		 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.

       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
", <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

       The following template can be used to perform processing in the directory specified by location and end up in the current working directory
       in use before the first cd command was issued:

	   cd location
	   if [ $? -ne 0 ]
	   then
	       print error message
	       exit 1
	   fi
	   ... do whatever is desired as long as the OLDPWD environment variable
	       is not modified
	   cd -

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 directory; 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 definition of dot-dot in most historical practice; that is, while this
       behavior has been optionally available in the KornShell, other shells have historically not supported this functionality. The logical path-
       name 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

       Section 2.12, Shell Execution Environment, pwd

       The Base Definitions volume of POSIX.1-2008, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines

       The System Interfaces volume of POSIX.1-2008, chdir()

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technol-
       ogy  --	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 Stan-
       dard 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								    CD(1P)