How do I find all files containing specific text on Linux ?

grep -rnw '/path/to/somewhere/' -e 'pattern'
     -r or -R is recursive,
     -n is line number, and
     -w stands for match the whole word.
     -l (lower-case L) can be added to just give the file name of matching files.

Along with these, --exclude, --include, --exclude-dir or --include-dir flags could be used for efficient searching:

This will only search through those files which have .c or .h extensions:
     grep --include=\*.{c,h} -rnw '/path/to/somewhere/' -e "pattern"

This will exclude searching all the files ending with .o extension:
     grep --exclude=*.o -rnw '/path/to/somewhere/' -e "pattern"

Just like exclude files, it is possible to exclude/include directories through --exclude-dir and --include-dir parameter. For example, this will exclude the dirs dir1/, dir2/ and all of them matching *.dst/:
     grep --exclude-dir={dir1,dir2,*.dst} -rnw '/path/to/somewhere/' -e "pattern"

eu folosesc

grep -nri “text” /abs/path