This is a small C program that prints an abbreviated representation of the
current working directory's path. It was designed to work with Bash's
PROMPT_COMMAND in
order to produce a terse PS1 prompt that includes the current working
directory path.
If I'm in the directory /home/alan/github/alandipert/prompt_pwd,
my Bash prompt will look like this:
alan@ubuntu:~/g/a/prompt_pwd$
Configuration similar to the following in your ~/.bashrc can be used:
PROMPT_COMMAND='PWD_ABBREV=$(prompt_pwd)'
PS1='\u@\h:${PWD_ABBREV}\$ '
make
sudo make install
By default, prompt_pwd will be installed to /usr/local/bin/prompt_pwd.
Thanks to Dave Yarwood for showing me Fish shell, the default prompt of
which inspired prompt_pwd.
Thank you also to Rainer Joswig for assistance with the original Common Lisp prototype.
prompt_pwd was originally prototyped in SBCL and later ported to C to improve its efficiency. The original Lisp code is below.
#!/usr/bin/sbcl --script
(defun split-string (str delim-char)
(loop for pos0 = -1 then pos1
for pos1 = (position delim-char str :start (1+ pos0))
collect (subseq str (1+ pos0) (or pos1 (length str)))
while pos1))
(defun abbreviate-butlast (path)
(loop for (item . rest) on path
collect (if (and rest (> (length item) 1))
(subseq item 0 1)
item)))
(defun abbreviate* (home-str cwd-str)
(let* ((cwd-path (split-string cwd-str #\/))
(home-path (split-string home-str #\/))
(home-shortened (if (eql 0 (search home-path cwd-path :test #'equalp))
(cons "~" (nthcdr (length home-path) cwd-path))
cwd-path)))
(format nil "~{~A~^/~}" (abbreviate-butlast home-shortened))))
(defun abbreviate (cwd-str)
(let* ((home-str (sb-ext:posix-getenv "HOME")))
(cond ((equal cwd-str home-str) "~")
((equal cwd-str "/") "/")
(t (abbreviate* home-str cwd-str)))))
(loop for line = (read-line nil nil nil)
while line
do (princ (abbreviate line)))prompt_pwd is distributed under the MIT
License, a copy of which is included in
the file LICENSE.