How to search an expression in a file from a bash script?

I have a bash script. I need to look if "text" exists in the file and do something if it exists.

Thanks in advance

From stackoverflow

• grep is your friend here

• Something like the following would do what you need.

  grep -w "text" file > /dev/null
  
  if [ $? -eq 0 ]; then
     #Do something
  else
     #Do something else
  fi
  

  Paul Creasey : I prefer `if [ $(grep -c "text" file) -gt 0 ]` but it the same thing.

  Gordon Davisson : Martin's approach (with `grep -q`) is both faster (doesn't search entire file, just up to the first match) and (IMHO) cleaner than either of these approaches.

• cat <file> | grep <"text"> and check the return code with test $?

  Check out the excellent: Advanced Bash-Scripting Guide

• If you need to execute a command on all files containing the text, you can combine grep with xargs. For example, this would remove all files containing "yourtext":

  grep -l "yourtext" * | xargs rm
  

  To search a single file, use if grep ...

  if grep -q "yourtext" yourfile ; then
    # Found
  fi
  

• You can put the grep inside the if statement, and you can use the -q flag to silence it.

  if grep -q "text" file; then
      :
  else
      :
  fi
  

• just use the shell

  while read -r line
  do
    case "$line" in
     *text* ) 
          echo "do something here"
          ;;
     * )  echo "text not found"
    esac
  done <"file"