Advanced Bash−Scripting Guide

t=${path_name%/*.*}
# Same effect as t=`dirname $path_name`
echo "path_name, stripped of suffixes = $t"
# These will fail in some cases, such as "../", "/foo////", # "foo/", "/".
# Removing suffixes, especially when the basename has no suffix,
#+ but the dirname does, also complicates matters.
# (Thanks, S.C.)
echo
t=${path_name:11}
echo "$path_name, with first 11 chars stripped off = $t"
t=${path_name:11:5}
echo "$path_name, with first 11 chars stripped off, length 5 = $t"
echo
Advanced Bash−Scripting Guide
t=${path_name/bozo/clown}
echo "$path_name with \"bozo\" replaced by \"clown\" = $t"
t=${path_name/today/}
echo "$path_name with \"today\" deleted = $t"
t=${path_name//o/O}
echo "$path_name with all o's capitalized = $t"
t=${path_name//o/}
echo "$path_name with all o's deleted = $t"
exit 0
${var/#Pattern/Replacement}
If prefix of var matches Pattern, then substitute Replacement for Pattern.
${var/%Pattern/Replacement}
If suffix of var matches Pattern, then substitute Replacement for Pattern.
Example 9−19. Matching patterns at prefix or suffix of string
#!/bin/bash
# Pattern replacement at prefix / suffix of string.
v0=abc1234zip1234abc
echo "v0 = $v0"
echo
# Original variable.
# abc1234zip1234abc
# Match at prefix (beginning) of string.
v1=${v0/#abc/ABCDEF} # abc1234zip1234abc
# |−|
echo "v1 = $v1"
# ABCDE1234zip1234abc
# |−−−|
# Match at suffix (end) of string.
v2=${v0/%abc/ABCDEF} # abc1234zip123abc
# |−|
echo "v2 = $v2"
# abc1234zip1234ABCDEF
# |−−−−|
echo
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
# Must match at beginning / end of string,
#+ otherwise no replacement results.
# −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
Chapter 9. Variables Revisited 91