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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 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 cur-
path 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 path-
name 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> charac-
ter 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 fol-
lows, 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 appropri-
ate 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 terminat-
ing null) and the directory operand was not longer than {PATH_MAX}
bytes (including the terminating null), then curpath shall be con-
verted 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 unspeci-
fied. 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 direc-
tory, 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 vari-
able is set, the OLDPWD environment variable shall also be set to the
value of the old working directory (that is the current working direc-
tory 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 compo-
nents 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 compo-
nents shall be resolved before dot-dot components are pro-
cessed (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
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 equiva-
lent 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 directo-
ries. 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 vari-
ables that are unset or null. (See the Base Definitions vol-
ume of POSIX.1-2008, 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 behav-
ior 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 direc-
tory 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 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
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 Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
cal 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 Standard
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.ker-
nel.org/doc/man-pages/reporting_bugs.html .
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