The /usr/bin/cd utility changes the current directory in the context of the cd utility only. This is in contrast to the version built into the shell, as described below. /usr/bin/cd has no effect on the invoking process but can be used to determine whether or not a given directory can be set as the current directory.

The Bourne shell built-in cd changes the current directory to argument. The shell parameter HOME is the default argument. The shell parameter CDPATH defines the search path for the directory containing argument. Alternative directory names are separated by a colon (:). The default path is <null> (specifying the current directory). Note: The current directory is specified by a null path name, which can appear immediately after the equal sign or between the colon delimiters anywhere else in the path list. If argument begins with `/', `.', or `.. ', the search path is not used. Otherwise, each directory in the path is searched for argument. cd must have execute (search) permission in argument. Because a new process is created to execute each command, cd would be ineffective if it were written as a normal command; therefore, it is recognized by and is internal to the shell. (See pwd(1), sh(1), and chdir(2)).

chdir is just another way to call cd.

If dir is not specified, the C shell built-in cd uses the value of shell parameter HOME as the new working directory. If dir specifies a complete path starting with ` / ', ` . ', or ` .. ', dir becomes the new working directory. If neither case applies, cd tries to find the designated directory relative to one of the paths specified by the CDPATH shell variable. CDPATH has the same syntax as, and similar semantics to, the PATH shell variable. cd must have execute (search) permission in dir. Because a new process is created to execute each command, cd would be ineffective if it were written as a normal command; therefore, it is recognized by and is internal to the C-shell. (See pwd(1), sh(1), and chdir(2)).

chdir changes the shell's working directory to directory dir. If no argument is given, change to the home directory of the user. If dir is a relative pathname not found in the current directory, check for it in those directories listed in the cdpath variable. If dir is the name of a shell variable whose value starts with a /, change to the directory named by that value.

pushd will push a directory onto the directory stack. With no arguments, exchange the top two elements.

+n

Rotate the n'th entry to the top of the stack and cd to it.

dir

Push the current working directory onto the stack and change to dir.

popd pops the directory stack and cd to the new top directory. The elements of the directory stack are numbered from 0 starting at the top.

+n

Discard the n'th entry in the stack.

dirs will print the directory stack, most recent to the left; the first directory shown is the current directory. With the -l argument, produce an unabbreviated printout; use of the ~ notation is suppressed.

The Korn shell built-in cd command can be in either of two forms. In the first form it changes the current directory to arg. If arg is - the directory is changed to the previous directory. The shell variable HOME is the default arg. The variable PWD is set to the current directory. The shell variable CDPATH defines the search path for the directory containing arg. Alternative directory names are separated by a colon (:). The default path is <null> (specifying the current directory). Note that the current directory is specified by a null path name, which can appear immediately after the equal sign or between the colon delimiters anywhere else in the path list. If arg begins with a ` / ', ` . ', or ` .. ', then the search path is not used. Otherwise, each directory in the path is searched for arg.

The second form of cd substitutes the string new for the string old in the current directory name, PWD and tries to change to this new directory.

The cd command may not be executed by rksh. Because a new process is created to execute each command, cd would be ineffective if it were written as a normal command; therefore, it is recognized by and is internal to the Korn shell. (See pwd(1), sh(1), and chdir(2)).