how can i compare strings in bash script?

Question

I need to compare a variable to some string (and do something if they match). How can i do the comparison?

Answer 1

Try this:

if [ "$x" == "valid" ]; then
  echo "x has the value 'valid'"
fi

If you want to do something when they don't match, replace == with !=. You want the quotes around $x, because if $x is empty, you'll get if [ == "valid" ]... which is a syntax error.

Answer 2

Or, if you don't need else clause:

[ "$x" == "valid" ] && echo "x has the value 'valid'"

Answer 3

you can also use use case/esac

case "$string" in
 "$pattern" ) echo "found";;
esac

Answer 4

if [ "$x" = "valid" ]; then
  echo "x has the value 'valid'"
fi

This is the solution if you are using Kourne Shell (ksh).Observe the single = where as in bash it should be ==