bashsyntaxparameter-expansion

Bash command on a variable

What does the following bash command do?

"${ctp// /}"

I want to check whether a variable is composed of an empty string or is all spaces, so that I can assign a default value.

Solution

  • It removes any space characters.

    Parameter Expansion expands parameters: $foo, $1. You can use it to perform string or array operations: "${file%.mp3}", "${0##*/}", "${files[@]: -4}". They should always be quoted.
    See: http://mywiki.wooledge.org/BashFAQ/073 and "Parameter Expansion" in man bash.
    Also see http://wiki.bash-hackers.org/syntax/pe