how to use grep to print just the matching expression and nothing else

new_2_unix · 01-07-2008, 05:01 PM

hi,

i'm trying to do a simple thing where, lets say i have:

Code:

$ echo "Hello World"  | grep "Hello"

>> Hello World

This works as expected, but is there a way I can print just the matching regular expression?

So in the above example, only "Hello" would print.

custangro · 01-07-2008, 05:08 PM

I would do it with sed...

Code:

echo "Hello World" | sed -e 's/World//g'

new_2_unix · 01-07-2008, 05:13 PM

this works in this example.
but it will not work as soon as the string changes to something else, for example "Hello World Once Again".

what i'm trying to do is that i have a line of HTML data, and i want to print just the selective HTML tags (and the text between them). i do not want to print the entire line.

any ideas on how i may do this will be much appreciated!

matthewg42 · 01-07-2008, 05:24 PM

Do you mean like the -o option (only matching)?

Code:

$ echo "hello world" |grep -o hello
hello

pixellany · 01-07-2008, 05:28 PM

sed -n 's/.*\(from\).*/\1/p' filename

Finds from anywhere in a line and prints it. Only works for one instance

Edit: Matthew's grep -o method looks to be better.

custangro · 01-07-2008, 06:02 PM

Quote:

Originally Posted by new_2_unix

this works in this example.
but it will not work as soon as the string changes to something else, for example "Hello World Once Again".

what i'm trying to do is that i have a line of HTML data, and i want to print just the selective HTML tags (and the text between them). i do not want to print the entire line.

any ideas on how i may do this will be much appreciated!

Now that I know this... I agree with pixellany grep -o would work better.

-C