Bash =~

Internal

• bash Concepts

Overview

The string to the right of the = ̃ operator is considered an extended regular expression and matched against the string to the left of the operator. The rules governing the extended regular expression are described in regex(3).

if [["string_to_be_matched_against_regex" =~ regex ]]; then
  # match 
else
  # no match 
fi

Usage is subject to the following constraints:

• The use of [[...]] is required.
• DO NOT use double quotes when specifying the regular expression, just specify the regex literal directly.
• If the regular expression contains spaces, use single quotes to denote space:

if [["something" =~ ${regex}' ' ]]; then ...

• Variable substitution works for both the string to be matched and the regular expression. When using a variable to specify the regular expression, do not enclose the variable in quotes, use it directly as in the example below:

if [[ "${var_containing_string_to_be_matched_against_regex}" =~ ${var_containing_regex} ]]; then ...