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cd - change the working directory
cd [-L | -P] [directory]
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 description of the algorithm used by cd. There is no requirement that curpath be made visible to the application.)
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.
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.
If the directory operand begins with a slash character, set curpath to the operand and proceed to step 7.
If the first component of the directory operand is dot or dot-dot, proceed to step 6.
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 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.
Set curpath to the string formed by the concatenation of the value of PWD , a slash character, and the operand.
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 directory 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 directory, the value of the PWD environment variable is unspecified. If the actions equivalent to chdir() fail for any reason, the cd utility 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.
The curpath value shall then be converted to canonical form as follows, considering each component from beginning to end, in sequence: <ol type="a">
Dot components and any slashes that separate them from the next component shall be deleted.
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.
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 single 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.
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 environment variable shall be set to curpath.
If, during the execution of the above steps, the PWD environment variable 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).
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:
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.
The following operands shall be supported:
cd "$OLDPWD" && pwd
which changes to the previous working directory and then writes its name.
The following environment variables shall affect the execution of cd:
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.
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
The working directory shall remain unchanged.
The following sections are informative.
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.
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.
Shell Execution Environment , pwd , the System Interfaces volume of IEEE Std 1003.1-2001, chdir()
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