root@ttsi.lonestar.org (System) (04/25/91)
A recent spate of articles (in comp.unix.shell) about pwd style
prompting and how to prune long paths piqued my interest. I got
to playing around and came up with a ksh / perl solution to pruning
long paths.
This produces ~ notation for home directory. So I get
~>
~/sub/dir>
instead of
//blast/user/mse>
//blast/user/mse/sub/dir>
(where blast is my node name). Paths not rooted from the home directory
convert to something like:
blast:/usr/local/src>
A really long path is shortened by successively pruning leading path
components until the length is less than a user-specified size.
Pruned components are replaced with "..." as in
blast:.../src/epoch-3.2>
The perl script 'prunepwd' below manages the pruning. I don't claim
this to be particularly efficient but on an Apollo 400, it takes about
a second of real time which is fast enough for me. Note my comments
in the definition of ksh function _cd below. I ran into inexplicable
runaway recursion (intermittently!) using the unalias approach.
Fortunately there is a published way to unalias by adding escaping
the alias with \.
Any suggestions for how to do this in ksh are welcome. Likewise for
improved perl code.
---
Mark S. Evans Tandem Telecommunications Systems Inc.
Phone: 214-516-6201 850 E. Central Parkway
Fax: 214-516-6801 Plano, TX 75074
Mail: mse@ttsi.lonestar.org
.kshrc definitions:
PWDSZ=25 # maximum prompt length
export PS1="`//blast/usr/local/bin/prunepwd $PWDSZ`\> "
alias cd=_cd
function _pwd {
PS1="`//blast/usr/local/bin/prunepwd $PWDSZ`\> "
}
function _cd {
# Ran into apparent Apollo (SR10.3) ksh bug here - unaliasing cd
# would intermittently fail to prevent recursion. Using
# backslash in the alias name revokes the alias.
# unalias cd # don't do this on Apollo
\cd $* # backslash prevents recursion on Apollo SR10.3
# alias cd=_cd # don't do this on Apollo
PS1="`//blast/usr/local/bin/prunepwd $PWDSZ`\> "
}
The perl script follows. Perl is available via anonymous ftp from
any site that archives gnu stuff. If you haven't tried it, you're
missing out on a great tool.
------------------------ snip from here to top --------------------------
#! /bin/sh
# This is a shell archive. Remove anything before this line, then unpack
# it by saving it into a file and typing "sh file". To overwrite existing
# files, type "sh file -c". You can also feed this as standard input via
# unshar, or by typing "sh <file", e.g.. If this archive is complete, you
# will see the following message at the end:
# "End of shell archive."
# Contents: prunepwd
# Wrapped by root@blast on Thu Apr 25 07:05:20 1991
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
if test -f 'prunepwd' -a "${1}" != "-c" ; then
echo shar: Will not clobber existing file \"'prunepwd'\"
else
echo shar: Extracting \"'prunepwd'\" \(2128 characters\)
sed "s/^X//" >'prunepwd' <<'END_OF_FILE'
X#!/usr/bin/perl
X##
X## prunepwd.pl - Prune a `pwd` string
X##
X## prunepwd prunes the current working directory path to a size that
X## is reasonable for a prompt. The size limit is specified by
X## optional command line argument. The default is 25.
X##
X## If the path is a descendent of the home directory path, the leading
X## home directory path is replaced with ``~''. Otherwise, a leading
X## //node_name (ala Apollo) is replaced with ``node_name:''.
X## Directories are trimmed from the beginning of the path (following
X## the node name) until the path length (including node name) is less
X## than the limit. The last directory in the path is never pruned,
X## even if its length exceeds the limit. The set of pruned
X## directories is replaced by ``...''.
X##
X## Examples:
X##
X## //blast/usr/abc/def/ghi/jkl/mno/pqr/stu/vwx (before)
X## blast:/.../pqr/stu/vwx (after)
X##
X## //blast/user/mse/learn/perl/chapter1 (before)
X## ~/learn/perl/chapter1 (after)
X##
X$pwdsz = shift || 25; # limit for pwd string
chop($cwd=`pwd`);
X$home=$ENV{'HOME'};
if ($cwd eq "//"){
X print $cwd;
X exit ();
X}
if (index ($cwd, $home) == 0) {
X $node = "";
X $cwd = "~" . substr ($cwd, length ($home));
X} else {
X if ($cwd =~ m|^//|) {
X ## Apollo style path (//node/path/...)
X ($node, $cwd) = ($cwd =~ m|//([^/]*)(.*)|o);
X $node .= ":";
X } else {
X ## Unix style path (/path/...)
X $node = "";
X }
X}
X$len = length ($node) + length ($cwd);
if ($len > $pwdsz) {
X @path = split (/\//, $cwd);
X ##
X ## always leave the final component of the path even if its
X ## length is greater than the limit.
X ##
X if ($#path > 1) {
X ##
X ## Find number of leading components in path to skip
X ##
X for ($skip = 0; $len > $pwdsz && $skip < ($#path); $skip++) {
X $len -= (length ($path[$skip]) + 1);
X if ($skip == 0) {
X $len += 3; # length of "..."
X }
X }
X $path[$skip-1] = "...";
X if ($skip > 1) {
X splice (@path, 0, $skip-1 );
X }
X }
X $cwd = join ("/", @path);
X}
print $node, $cwd;
X
END_OF_FILE
if test 2128 -ne `wc -c <'prunepwd'`; then
echo shar: \"'prunepwd'\" unpacked with wrong size!
fi
chmod +x 'prunepwd'
# end of 'prunepwd'
fi
echo shar: End of shell archive.
exit 0
--
Mark S. Evans Tandem Telecommunications Systems Inc.
Phone: 214-516-6201 850 E. Central Parkway
Fax: 214-516-6801 Plano, TX 75074
Mail: mse@ttsi.lonestar.orgdave@aspect.UUCP (Dave Corcoran) (05/09/91)
In article <1991Apr25.122017.3868@ttsi.lonestar.org>, root@ttsi.lonestar.org (System) writes: > A recent spate of articles (in comp.unix.shell) about pwd style Which I missed so forgive me if this has been proposed. > A really long path is shortened by successively pruning leading path > components until the length is less than a user-specified size. > Pruned components are replaced with "..." as in > Any suggestions for how to do this in ksh are welcome. Likewise for > improved perl code. Although this will not limit of the prompt to a specified size it is terse. PS1='${PWD#$HOME/}' You could substitute $DIR for $HOME and then set DIR to the leading path you want trimmed. -- David Corcoran -@@ uunet!aspect!dave ~ Having the right to do something is not the same as being right in doing it. -- C.K. Chesterson