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



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

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 Environment)
       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 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 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>
               characters, 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.1-2017, 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-minus> 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.1-2017, 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\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
       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
       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
       Section 2.12, Shell Execution Environment, pwd

       The Base Definitions volume of POSIX.1-2017, Chapter _8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

       The System Interfaces volume of POSIX.1-2017, chdir()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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                  2017                                CD(1)
