Advanced Bash−Scripting Guide

Advanced Bash−Scripting Guide
var01=abcdEFGH28ij
echo "var01 = ${var01}"
echo "Length of var01 = ${#var01}"
echo "Number of command−line arguments passed to script = ${#@}"
echo "Number of command−line arguments passed to script = ${#*}"
exit 0
${var#Pattern}, ${var##Pattern}
Remove from $var the shortest/longest part of $Pattern that matches the front end of $var.
A usage illustration from Example A−8:
# Function from "days−between.sh" example.
# Strips leading zero(s) from argument passed.
strip_leading_zero () # Better to strip possible leading zero(s)
{ # from day and/or month
val=${1#0}
# since otherwise Bash will interpret them
return $val # as octal values (POSIX.2, sect 2.9.2.1).
}
Another usage illustration:
echo `basename $PWD`
echo "${PWD##*/}"
echo
echo `basename $0`
echo $0
echo "${0##*/}"
echo
filename=test.data
echo "${filename##*.}"
# Basename of current working directory.
# Basename of current working directory.
# Name of script.
# Name of script.
# Name of script.
# data
# Extension of filename.
${var%Pattern}, ${var%%Pattern}
Remove from $var the shortest/longest part of $Pattern that matches the back end of $var.
Version 2 of Bash adds additional options.
Example 9−16. Pattern matching in parameter substitution
#!/bin/bash
# Pattern matching using the # ## % %% parameter substitution operators.
var1=abcd12345abc6789
pattern1=a*c # * (wild card) matches everything between a − c.
echo
echo "var1 = $var1"
# abcd12345abc6789
echo "var1 = ${var1}" # abcd12345abc6789 (alternate form)
echo "Number of characters in ${var1} = ${#var1}"
echo "pattern1 = $pattern1" # a*c (everything between 'a' and 'c')
echo
Chapter 9. Variables Revisited 88