String Manipulation 字串處理

my_string="abhishek"
echo "length is ${#my_string}"

Using expr

str="my string"
length=$(expr length "$str")
echo "Length of my string is $length"

Using awk

echo "my string" | awk '{print length}'

Using wc

str="my string"
length=$(echo -n "my string" | wc -m)
echo "Length of my string is $length"

Using wildcards

#!/bin/bash

STR='GNU/Linux is an operating system'
SUB='Linux'
if [[ "$STR" == *"$SUB"* ]]; then
  echo "It's there."
fi

Using case

#!/bin/bash

STR='GNU/Linux is an operating system'
SUB='Linux'

case $STR in

  *"$SUB"*)
    echo -n "It's there."
    ;;
esac

Using Regex

#!/bin/bash

STR='GNU/Linux is an operating system'
SUB='Linux'

if [[ "$STR" =~ .*"$SUB".* ]]; then
  echo "It's there."
fi

Using Grep

#!/bin/bash

STR='GNU/Linux is an operating system'
SUB='Linux'

if grep -q "$SUB" <<< "$STR"; then
  echo "It's there"
fi

str1="hand"
str2="book"
str3=$str1$str2

foss="Fedora is a free operating system"
echo ${foss:0:6}

foss="Fedora is a free operating system"
echo ${foss/Fedora/Ubuntu}

`${parameter:-defaultValue}`	Get default shell variables value
`${parameter:=defaultValue}`	Set default shell variables value
`${parameter:?"Error Message"}`	Display an error message if parameter is not set
`${#var}`	Find the length of the string
`${var%pattern}`	Remove from shortest rear (end) pattern
`${var%%pattern}`	Remove from longest rear (end) pattern
`${var:num1:num2}`	Substring
`${var#pattern}`	Remove from shortest front pattern
`${var##pattern}`	Remove from longest front pattern
`${var/pattern/string}`	Find and replace (only replace first occurrence)
`${var//pattern/string}`	Find and replace all occurrences
`${!prefix*}`	Expands to the names of variables whose names begin with prefix.
`${var,}` `${var,pattern}`	Convert first character to lowercase.
`${var,,}` `${var,,pattern}`	Convert all characters to lowercase.
`${var^}` `${var^pattern}`	Convert first character to uppercase.
`${var^^}` `${var^^pattern}`	Convert all character to uppercase.