Shell Programming and Scripting

 
grep -F $string file
grep -x $string file
grep "^${string}$" file
awk '/"${string}"/ {print $0}' file

 
while read string
do 
 <above commands>
done < file

grep -F $string file                 # The variable needs to be put in double quotes 
grep -x $string file                 # This is a whole line match, but $string is interpreted as a regex 
                                     # and the variable needs to be put in double quotes 
grep "^${string}$" file              # This is a whole line match, but $string is interpreted as a regex
awk '/"${string}"/ {print $0}' file  # This will not work, see RudiC's comments