grep -rnw 'directory' -e "pattern"

-r is recursive, -n is line number and -w stands match the whole word. Along with these, --exclude or --include parameter could be used for efficient searching. Something like below:

grep --include=\*.{c,h} -rnw 'directory' -e "pattern"

This will only search through the files which have .c or .h extensions. Similarly a sample use of --exclude:

grep --exclude=*.o -rnw 'directory' -e "pattern"

Above will exclude searching all the files ending with .o extension. Just like exclude file it's possible to exclude/include directories through --exclude-dir and --include-dir parameter, the following shows how to integrate --exclude-dir:

grep --exclude-dir={dir1,dir2,*.dst} -rnw 'directory' -e "pattern"