[SOLVED] difference between 'grep "\n" * | wc -l' and 'wc -l *' total count

vendtagain · 10-12-2010, 07:11 PM

I am trying to find the number of lines in a directory containing .h and .cpp files.
When I type

Code:

grep "\n" * | wc -l

this prints about 2000.

Code:

wc -l *

The total count that this prints is nearly twice as much, about 4000. From reading man pages, it seems that both of these should print the same number, the number of lines in the files, but they are definitely not equal.

Meson · 10-12-2010, 07:33 PM

The grep one isn't doing what you think it is. Try doing it with the pipe. You have 2000 lines that contain the letter n.

Tinkster · 10-12-2010, 07:42 PM

Indeed ... grep "\n" doesn't grep for newlines. If you want that
you need to do

Code:

grep -E '$' *

vendtagain · 10-12-2010, 08:30 PM

Quote:

Originally Posted by Tinkster

Indeed ... grep "\n" doesn't grep for newlines. If you want that
you need to do

Code:

grep -E '$' *

Thanks Tinkster, this worked correctly.

Quote:

The grep one isn't doing what you think it is. Try doing it with the pipe. You have 2000 lines that contain the letter n.

You are right, I checked grep with "n" instead of "\n" and it produced the same results, I guess it ignores the backslash..

Tinkster · 10-12-2010, 08:32 PM

Quote:

Originally Posted by vendtagain

Thanks Tinkster, this worked correctly.

You are right, I checked grep with "n" instead of "\n" and it produced the same results, I guess it ignores the backslash..

Yup, it does. As far as regular expressions go \n has
no meaning, so the escape just gets dropped.

Well - it does have a meaning as in back-referencing, but
that's not what you were doing (or trying to do).

Cheers,
Tink