count number of lines, bash grep

Question

Hello I am grepping results to file, and then doing cat to show its content on the screen, I want to know how many lines of results I have in my results file and the += it to some counter.

What will be the best way? Any relevant flag to grep or cat?

Answer 1

If you have already collected the grep() output in a file, you could output a numbered list with:

cat -n myfile

If you only want the number of lines, simply do:

wc -l myfile

There is absolutely no reason to do:

cat myfile | wc -l

...as this needlessly does I/O (the 'cat') that wc() has to repeat. Besides, you have two processes where one suffices.

If you want to grep() to your terminal and print a count of the matches at the end, you can do:

grep whatever myfile | tee /dev/tty | wc -l

Answer 2

The -c flag will do the job.

For example:

 grep -c ^ filename

will cont the lines

Answer 3

Use

your_command | wc -l

From the manual:

NAME
       wc - print newline, word, and byte counts for each file

...

       -l, --lines
          print the newline counts

Answer 4

You can use wc -l to get line count.

Example:

$ cat foobar.txt | wc -l