If you just want to find files with a certain name, use find

The man page can be found HERE or by typing man find at the terminal prompt.

Basically, find will recursively look for a file meeting criteria you specify. The easiest example:

find . -name file_name -print

That will search for a file named "file_name" starting in the current directory and searching below and print the files with that name.

find ~ -name ".DS_Store" -delete

That will find all the .DS_Store files and delete them.

You can search by name, regex, date. You can act on the file in any Unix way with the -exec predicate.

You can also use find as the start of a more complex pipeline of actions. Example:

find . -type f -print | egrep -i '\.m4a$|\.mp3$'

Will find all the files with extensions .m4a or .mp3

find . -type f -print | egrep -i '\.m4a$|\.mp3$' | wc -l

Will give you a count of those files.

If you want to search through a whole folder, just use -r on grep:

grep -r pattern folder/to/search

With find, you can also use xargs:

find folder/to/search -name '*.txt' | xargs grep pattern

or to make sure that you search two files at a time and therefore have the filenames specified:

find folder/to/search -name '*.txt' | xargs grep -n2 pattern

grep expects both a pattern and a filespec. If one is missing then it uses what is passed as the pattern, and waits for the data to search via standard input.

If you want to use a more complex filespec then use find.

find ~ -name '*.txt' -exec grep -q 'secret' {} \; -print