How to check if a file contains a specific string

Question

I want to check if a file contains a specific string or not in bash. I used this script, but it doesn't work:

 if [[ 'grep 'SomeString' $File' ]];then
   # Some Actions
 fi

What's wrong in my code?

Answer 1

In case you want to checkif the string matches the whole line and if it is a fixed string, You can do it this way

grep -Fxq [String] [filePath]

example

 searchString="Hello World"
 file="./test.log"
 if grep -Fxq "$searchString" $file
    then
            echo "String found in $file"
    else
            echo "String not found in $file"
 fi

From the man file:

-F, --fixed-strings

          Interpret  PATTERN  as  a  list of fixed strings, separated by newlines, any of 

which is to be matched.
          (-F is specified by POSIX.)
-x, --line-regexp
          Select only those matches that exactly match the whole line.  (-x is specified by 

POSIX.)
-q, --quiet, --silent
          Quiet; do not write anything to standard output.  Exit immediately with zero 

status  if  any  match  is
          found,  even  if  an error was detected.  Also see the -s or --no-messages 

option.  (-q is specified by
          POSIX.)

Answer 2

In addition to other answers, which told you how to do what you wanted, I try to explain what was wrong (which is what you wanted.

In Bash, if is to be followed with a command. If the exit code of this command is equal to 0, then the then part is executed, else the else part if any is executed.

You can do that with any command as explained in other answers: if /bin/true; then ...; fi

[[ is an internal bash command dedicated to some tests, like file existence, variable comparisons. Similarly [ is an external command (it is located typically in /usr/bin/[) that performs roughly the same tests but needs ] as a final argument, which is why ] must be padded with a space on the left, which is not the case with ]].

Here you needn't [[ nor [.

Another thing is the way you quote things. In bash, there is only one case where pairs of quotes do nest, it is "$(command "argument")". But in 'grep 'SomeString' $File' you have only one word, because 'grep ' is a quoted unit, which is concatenated with SomeString and then again concatenated with ' $File'. The variable $File is not even replaced with its value because of the use of single quotes. The proper way to do that is grep 'SomeString' "$File".

Answer 3

grep -q [PATTERN] [FILE] && echo $?

The exit status is 0 (true) if the pattern was found;

Answer 4

I done this, seems to work fine

if grep $SearchTerm $FileToSearch; then
   echo "$SearchTerm found OK"
else
   echo "$SearchTerm not found"
fi

Answer 5

if grep -q [string] [filename]
then
    [whatever action]
fi

Example

if grep -q 'my cat is in a tree' /tmp/cat.txt
then
    mkdir cat
fi

Answer 6

Try this:

if [[ $(grep "SomeString" $File) ]] ; then
   echo "Found"
else
   echo "Not Found"
fi