BASH Trick: check variant if contains some string

bash trick: build-in method

A="abcd0123456789"
if [ "${A/1234/}" != "$A" ] ; then
  echo yes
fi

grep method

A="abcd0123456789"
if echo $A | grep -q 1234 ; then
  echo yes
fi

After I test, 1st method is 40 times faster then grep method