Advanced Bash−Scripting Guide

Example 5−1. Echoing Weird Variables
Advanced Bash−Scripting Guide
#!/bin/bash
# weirdvars.sh: Echoing weird variables.
var="'(]\\{}\$\""
echo $var # '(]\{}$"
echo "$var" # '(]\{}$" Doesn't make a difference.
echo
IFS='\'
echo $var # '(] {}$" \ converted to space.
echo "$var" # '(]\{}$"
# Examples above supplied by S.C.
exit 0
Single quotes (' ') operate similarly to double quotes, but do not permit referencing variables, since the special
meaning of $ is turned off. Within single quotes, every special character except ' gets interpreted literally.
Consider single quotes ("full quoting") to be a stricter method of quoting than double quotes ("partial
quoting").
Since even the escape character (\) gets a literal interpretation within single quotes, trying to enclose
a single quote within single quotes will not yield the expected result.
echo "Why can't I write 's between single quotes"
echo
# The roundabout method.
echo 'Why can'\''t I write '"'"'s between single quotes'
# |−−−−−−−| |−−−−−−−−−−| |−−−−−−−−−−−−−−−−−−−−−−−|
# Three single−quoted strings, with escaped and quoted single quotes between.
# This example courtesy of Stephane Chazelas.
Escaping is a method of quoting single characters. The escape (\) preceding a character tells the shell to
interpret that character literally.
With certain commands and utilities, such as echo and sed, escaping a character may have the opposite
effect − it can toggle on a special meaning for that character.
Special meanings of certain escaped characters
used with echo and sed
\n
means newline
\r
means return
\t
means tab
\v
means vertical tab
Chapter 5. Quoting 33