follows:
Click here to view code image
matthew@seymour:~$ grep -r "some text" *
Each time a string is matched within a file, the filename and the match are
printed. If a file contains multiple matches, each of the matches is printed.
You can alter this behavior with the -l parameter (lowercase L), which forces
grep to print the name of each file that contains at least one match without
printing the matching text. If a file contains more than one match, it is still
printed only once. Alternatively, the -c parameter prints each filename that
was searched and includes the number of matches at the end, even if there
were no matches.
You have a lot of control when specifying the pattern to search for. You can,
as shown previously, specify a simple string like some text, or you can
invert that search by specifying the -v parameter. For example, the following
returns all the lines of the file myfile.txt that do not contain the word
hello:
Click here to view code image
matthew@seymour:~$ grep -v "hello" myfile.txt
You can also use regular expressions for search terms. For example, you can
search myfile.txt for all references to cat, sat, or mat with this command:
Click here to view code image
matthew@seymour:~$ grep "[cms]at" myfile.txt
Adding the -i parameter to this removes case-sensitivity, matching Cat, CAT,
MaT, and so on:
Click here to view code image
matthew@seymour:~$ grep -i [cms]at myfile.txt
You can also control the output to some extent with the -n and —color
parameters. The first tells grep to print the line number for each match,
which is where it appears in the source file. The —color parameter tells
grep to color the search terms in the output, which helps them stand out
from among all the other text on the line. You choose which color you want
by using the GREP_COLOR environment variable; for example, export
GREP_COLOR=36 gives you cyan, and export GREP_COLOR=32 gives
you lime green.
This next example show how to use these two parameters to number and
color all matches to the previous command: