replace dots in a string with a character in bash

Question

i have a string like 1.1.1.1.1 , i want to replace all dots with _ character.

i wrote the following program:

#!/bin/bash

var="1.1.1.1.1"
new2=${var/./_}
echo $new2

but it just replaces first dot with _ in the string, so the result is: 1_1.1.1.1

how i can replace all dots with _ ?

thanks.

Answer 1

You were pretty close. To replace all matches, use ${var//find/replace}:

#!/bin/bash
var="1.1.1.1.1"
new2="${var//./_}"
echo "$new2"       # prints 1_1_1_1_1

The bash built-ins of the form ${var...} are called parameter expansions/substitutions. They are documented in detail in the official bash manual. For an alternative explanation, check out bash-hackers.org.