[SOLVED] Grep doesn't read stdin?

littlebigman · 06-05-2015, 04:57 PM

Hello

I'm no regex/grep expert, and having a bit of a problem getting grep to read data from stdin.

This works:

Code:

grep -Pzo "(?s)(?<=<title>\n)(.*)(?=</title>)" input.html

This prints nothing, although the Internet says that grep reads stdin unless told to read from a file:

Code:

wget -qO- 'http://www.acme.com/index.html' -so - | grep -Pzo "(?s)(?<=<title>)(.*)(?=</title>)"

Any idea why?

FWIW, it's GNU grep 2.12 running on Debian.

Thank you.

Keith Hedger · 06-05-2015, 06:03 PM

Try

Code:

keithhedger@severnet /tmp/xx $ wget -qO- 'http://www.acme.com/index.html' -O - | grep -Pzo "(?s)(?<=<title>)(.*)(?=</title>)"
ACME Laboratories

There is no 's' option and it should be a capital 'O' to set the output file name.

littlebigman · 06-10-2015, 08:06 AM

Thanks.

I used the following successfully:

Code:

wget 'http://www.acme.com/index.html' -qO - | grep -Pzo '(?s)(?<=<title>)(.*)(?=</title>)' > output.html

The "(?s)" option is to tell grep to support multine mode, while "(?<=" and "(?=" is so that those bits between brackets are ignored in the output.