String
Operators
  • =, equal
  • !=, not equal
  • -z, checks if the given string operand size is zero
  • -n, checks if the given string operand size is non-zero
  • str, if str is empty, return false
    • #!/bin/bash

a="abc"
b="def"

if [ ! $a = $b ]
then
	echo "Not same ..."
fi

if [ -n $a ]
then
	echo "Size is none zero ..."
fi
    String manipulation
    #!/bin/bash

a="abc"

# length
echo "Size: ${#a}"
echo `expr length $a`

# match substring at the beginning of string
stringZ=abcABC123ABCabc
echo `expr match "$stringZ" 'abc[A-Z]*.2'` # 8

# index of substring in string
echo `expr index "$stringZ" C12` # 6

# Substring Extraction
# ${string:position}
# ${string:position:length}
echo ${stringZ:1} # bcABC123ABCabc
echo ${stringZ:7:3} # 23A
echo ${stringZ:(-4)} # Cabc
# expr substr $string $position $length
echo `expr substr $stringZ 1 2` # ab
# expr match "$string" '\($substring\)'
echo `expr match "$stringZ" '\(.[b-c]*[A-Z]..[0-9]\)'` # bcABC1
echo `expr "$stringZ" : '\(.[b-c]*[A-Z]..[0-9]\)'`     # abcABC1

# Substring Removal
# ${string#substring}, deletes shortest match of $substring from front of $string
echo ${stringZ#a*C} # 123ABCabc
# ${string##substring}, deletes longest match of $substring from front of $string
echo ${stringZ##a*C}     # abc
# ${string%substring}, deletes shortest match of $substring from back of $string
# ${string%%substring}, deletes longest match of $substring from back of $string

# Substring Replacement
# ${string/substring/replacement}, replace the first match
echo ${stringZ/abc/xyz} # xyzABC123ABCabc
# ${string//substring/replacement}, replace all matches
echo ${stringZ//abc/xyz}      # xyzABC123ABCxyz
# ${string/#substring/replacement}, If $substring matches front end of $string, substitute $replacement for $substring
echo ${stringZ/#abc/XYZ}          # XYZABC123ABCabc
# ${string/%substring/replacement}, If $substring matches back end of $string, substitute $replacement for $substring
echo ${stringZ/%abc/XYZ}          # abcABC123ABCXYZ
    Reference