The command you are looking for is strings
Its name is quite self-explanatory, it retrieves any printable string from a given file.
man strings
gives:
STRINGS(1)
NAME
strings – find the printable strings in a object, or other binary, fileSYNOPSIS
strings [ - ] [ -a ] [ -o ] [ -t format ] [ -number ] [ -n number ] [--] [file ...]