You can do either of
grep pattern_search . # does a normal grep on the current directory
grep pattern_search * # use a normal grep on all the globbed files from the current directory
grep -R pattern_search . # use a recursive search on the current directory
grep -H pattern_search * # prints filename when the files are more than one. ‘-H’
Other options such as (from gnu manual):
If an input file is a directory, use action to process it. By default,
action is ‘read’, which means that directories are read just as if they
were ordinary files (some operating systems and file systems disallow
this, and will cause grep to print error messages for every directory
or silently skip them). If action is ‘skip’, directories are silently
skipped. If action is ‘recurse’, grep reads all files under each
directory, recursively; this is equivalent to the ‘-r’ option.
Skip files whose base name matches glob (using wildcard matching). A
file-name glob can use ‘*’, ‘?’, and ‘[’...‘]’ as wildcards, and \ to
quote a wildcard or backslash character literally.
Skip files whose base name matches any of the file-name globs read from
file (using wildcard matching as described under ‘--exclude’).
Exclude directories matching the pattern dir from recursive directory
Process a binary file as if it did not contain matching data; this is
equivalent to the ‘--binary-files=without-match’ option.
Search only files whose base name matches glob (using wildcard matching
as described under ‘--exclude’).
For each directory mentioned on the command line, read and process all
files in that directory, recursively. This is the same as the
Print the file name for each match. This is the default when there is
more than one file to search.