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)
Linux-Distributionen
Huschi als Linux-Admin