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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  corresponding
       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 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(1P)
 

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