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Previous: 7.10 What Good Is a Blank Shell Prompt? Chapter 7
Setting Your Shell Prompt
Next: 7.12 External Commands Send Signals to Set Variables

7.11 dirs in Your Prompt: Better than $cwd

The C shell gives the absolute pathname of your current directory in $cwd (14.13 ) . Many people use that in their prompts. If you use the pushd and popd (14.6 ) commands, you may not always remember exactly what's in your directory stack (I don't, at least). Also, do you want to shorten your home directory pathname to just a tilde (~ ) so it takes less room in the prompt? Here's how: run the dirs command and use its output in your prompt. A simple alias for cd users looks like this:

alias cd 'chdir \!* && set prompt="`dirs`% "'

and the prompts look like:

/work/project % cd

~ % cd bin

~/bin %

Here's what to put in .cshrc to make a multiline prompt (7.5 ) that shows the directory stack:

uname -n

# PUT hostname.domain.name IN $hostname AND hostname IN $HOST:
set hostname=`uname -n`
setenv HOST `expr $hostname : '\([^.]*\).*'`

alias setprompt 'set prompt="\\
${USER}@${HOST} `dirs`\\
\! % "'
alias cd  'chdir \!* && setprompt'
alias pushd  'pushd \!* && setprompt'
alias popd  'popd  \!* && setprompt'

Because bash can run a command each time it sets its prompt, and because it has built-in prompt operators (7.4 ) , the bash version of all the stuff above fits on one line:

PS1='\n\u@\h $(dirs)\n\! \$ '

That makes a blank line before each prompt; if you don't want that, join the first and second lines of the setprompt alias or remove the first \n . Let's push a couple of directories and watch the prompt:

jerry@ora ~
1 % pushd /work/src/perl

/work/src/perl ~

jerry@ora /work/src/perl ~
2 % cd ../cnews

jerry@ora /work/src/cnews ~
3 % pushd ~/bin

~/bin /work/src/cnews ~

jerry@ora ~/bin /work/src/cnews ~
4 %

Warning! Of course, the prompt looks a little redundant there because each pushd command also shows the dirs output. A few commands later, though, having your directory stack in the prompt will be handy. If your directory stack has a lot of entries, the first line of the prompt can get wider than the screen. In that case, store the dirs output in a shell array (47.5 ) and edit it with a command like sed or with the built-in csh string editing (9.6 ) .

For example, to show just the tail of each path in the dirs output, use the alias below; the C shell operator :gt globally edits all words, to the tail of each pathname:

alias setprompt 'set dirs=(`dirs`); set prompt="\\
${USER}@${HOST} $dirs:gt\\
\! % "'

Watch the prompt. If you forget what the names in the prompt mean, just type dirs :

jerry@ora bin cnews jerry
5 % pushd ~/tmp/test

~/tmp/test ~/bin /work/src/cnews ~
jerry@ora test bin cnews jerry
12 % dirs

~/tmp/test ~/bin /work/src/cnews ~

There's a related tip in article 47.5 : storing the directory stack in an array variable.

- JP

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