How to check if a string contains a substring in Bash

Asked 2008-10-23T12:37:31.787

3662

I have a string in Bash:

string="My string"

How can I test if it contains another string?

if [ $string ?? 'foo' ]; then
  echo "It's there!"
fi

Where ?? is my unknown operator. Do I use echo and grep?

if echo "$string" | grep 'foo'; then
  echo "It's there!"
fi

That looks a bit clumsy.

Edit Report

1 Answer

108

The accepted answer is best, but since there's more than one way to do it, here's another solution:

if [ "$string" != "${string/foo/}" ]; then
    echo "It's there!"
fi

${var/search/replace} is $var with the first instance of search replaced by replace, if it is found (it doesn't change $var). If you try to replace foo by nothing, and the string has changed, then obviously foo was found.

answered 2008-10-23T14:35:45.400

How to check if a string contains a substring in Bash

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