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14.5 Saving Time When You Change Directories: cdpath

Some people make a shell alias ( 10.2 ) for directories they cd to often. Other people set shell variables ( 6.8 ) to hold the pathnames of directories they don't want to retype. But both of those methods make you remember directory abbreviations - and make you put new aliases or shell variables in .cshrc or .profile each time you want to add or change one. There's an easier way: the C shell's cdpath shell variable and the CDPATH variable in ksh , bash , and some versions of sh . I'll use the term "cdpath" to talk about all shells.

When you type the command cd   foo , the shell first tries to go to the exact pathname foo . If that doesn't work, and if foo is a relative pathname, the shell tries the same command from every directory listed in the cdpath . (If you use ksh or sh , see the note at the end of this article.)

Let's say that your home directory is /home/lisa and your current directory is somewhere else. Let's also say that your cdpath has the directories /home/lisa , /home/lisa/projects , and /books/troff . If your cd   foo command doesn't work in your current directory, then your shell will try cd /home/lisa/ foo , cd /home/lisa/projects/ foo , and cd /books/troff/ foo , in that order. If the shell finds one, it shows the pathname:


cd foo


Some Bourne shells don't show the directory name. All shells print an error, though, if they can't find any foo directory.

So, set your cdpath to a list of the parent directories that contain directories you might want to cd to. Don't list the exact directories - list the parent directories ( 1.21 ) . This list goes in your .cshrc or .profile file. For example, lisa 's .cshrc could have:


set cdpath=(~ ~/projects /books/troff)

A Bourne shell user would have this in .profile :

export CDPATH

(If your system doesn't define $HOME , try $LOGDIR .)

NOTE: Note that the Bourne shell CDPATH in the above example starts with a colon ( : )-which, as in the PATH variable, is actually an empty entry ( 6.4 ) that stands for "the current directory." Both the sh and ksh I tested required that. Without an empty entry, neither sh or ksh would cd into the current directory! ( bash seemed to work like csh , though.) You could actually call this a feature. If there's no empty entry in CDPATH , a user has to use cd  ./subdirname to go to a subdirectory of the current directory.

- JP

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