#!/bin/bash

# This script takes the $PWD string and truncates it
# to a set percentage of the terminal width.
# It's designed to be used in the bash $PS1 prompt to keep it
# from taking up too much space, but it may be useful for
# other purposes too, of course.  There may be minor variations
# in the actual length owing to rounding in the arithmetic
# functions.  The most current version can be found here:

http://www.linuxquestions.org/questions/showthread.php?p=3396562#post3396562


# Usage:  Put the script in a convenient location, such as
# /usr/local/bin, make it executable and set $PS1 in your
# .bashrc or similar file in this manner:
#
#     shopt -s checkwinsize
#     export PS1='\u:$(/usr/local/bin/variprompt.sh $COLUMNS)$ '
#
# Note the single quotes.  Double quotes will not work.
# The shopt command ensures that the $COLUMNS variable is set
# in the terminal.  If you don't include the $COLUMNS variable
# here, then the script will not be able to dynamically adjust
# to the width, and the target percentage setting will behave
# as a fixed-length string instead ($COLUMNS will default to
# 100).

# Set the desired width of the prompt below as the percentage
# of the total terminal width you want the path part of the
# prompt to take up.  Remember that any other parts you add to
# the prompt (such as username) will take up additional space.
# Also be aware that this script is designed for reasonable
# numbers, and may act in unpredictable ways if the target
# and/or terminal width are very small.  Target values under
# 20 are not recommended.


TARGETPCT=50

# (Hint: make it "$2" and you can set the target from
# within the PS1 prompt command instead, right after $COLUMNS.)


# The columns variable isn't readable from within the script.
# It must be fed in from outside.  If missing, a default of
# 100 will be set.


COLUMNS=${1:-100}


# Modify the $PWD to collapse "$HOME" into "~".  Simply
# replace this value with '$PWD' if this behavior is unwanted.


CURRENTDIR="${PWD/#$HOME/~}"


# Determine the number of characters in the
# modified $PWD string.


CURRENTLENGTH="${#CURRENTDIR}"


# Calculate the target length and the sizes
# of the starting and ending segments.


TARGETLENGTH="$((COLUMNS*TARGETPCT/100))"
FIRSTPART="$((TARGETLENGTH/3-3))"
LASTPART="$((CURRENTLENGTH-(TARGETLENGTH*2/3)))"


# Finally we compare the current length of the prompt
# to the target length and print the appropriate output string.


if [ "$CURRENTLENGTH" -le "$TARGETLENGTH" ]; then

# No modifications are necessary if less than the target length.
# Print the unmodified string.

	echo "$CURRENTDIR"

else

# Very small target or column values can make "FIRSTPART"
# come out to zero or less.  So test it to avoid throwing out
# an error, and set it to display only the first two characters
# of the string in such situations.
# Otherwise, print the desired truncated string. 


	if [ "$FIRSTPART" -gt "1" ]; then

		echo "${CURRENTDIR:0:$FIRSTPART}...${CURRENTDIR:$LASTPART}"

	else

		echo "${CURRENTDIR:0:2}...${CURRENTDIR:$LASTPART}"

	fi

fi

# All finished.

exit 0

export PS1='\u:$(/usr/local/bin/variprompt.sh $COLUMNS)$ '

One of the first two characters sometimes won't display, for example.

if [ "$FIRSTPART" -gt "1" ]; then ...

#!/bin/ksh -fu
#
v_wd=$(pwd)
if [ ${#v_wd} -gt 30 ] ; then
  echo ${v_wd} | sed -e 's!\(...............\).*\(...............\)!\1 ... \2!'
else
  echo ${v_wd}
fi
#

export PS1="\h:\$(/usr/local/bin/pwd30)<\!>$ "

@@ -54,7 +54,7 @@
 # replace this value with '$PWD' if this behavior is unwanted.
 
 
-CURRENTDIR="${PWD/#$HOME/~}"
+CURRENTDIR="${PWD/#$HOME/"~"}"