grep -q "something" file
[[ !? -eq 0 ]] && echo "yes" || echo "no"

##To check for a particular  string in a file

cd PATH_TO_YOUR_DIRECTORY #Changing directory to your working directory
File=YOUR_FILENAME  
if grep -q STRING_YOU_ARE_CHECKING_FOR "$File"; ##note the space after the string you are searching for
then
echo "Hooray!!It's available"
else
echo "Oops!!Not available"
fi

如果你想检查字符串是否匹配整行，如果它是一个固定的字符串，你可以这样做

grep -Fxq [String] [filePath]

例子

 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

从男子档案中可以看出:

-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.)

如果您想检查文件是否不包含特定的字符串，您可以按照以下方法进行检查。

if ! grep -q SomeString "$File"; then
  Some Actions # SomeString was not found
fi

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

如果找到模式，则退出状态为0 (true);否则blankstring。

试试这个:

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