I'm trying to use grep to get the line number only. This is the command I'm using:
grep -n "Content-Disposition: attachment" mbox
The output I get is:
45:Content-Disposition: attachment; filename="test.txt"
So now I just want to get the line number (45) from this output.
Can someone help me with this? Thanks
grep -n "Content-Disposition: attachment" mbox | sed -n 's/^\([0-9]*\)[:].*/\1/p'
Thanks. That worked exactly how I needed it to. If you don't mind, can you explain what this means for me so I know in the future:
's/^\([0-9]*\)[:].*/ \ 1/p'
Thanks a lot.
You'll need to read up on regular expressions to really make much use of it, but here it is anyway:
The -n means not to print anything unless it's explicitly requested.
s - substitute
/ - beginning of patter to match
^ - The null character at the start of the line
\(....\) - store this in the pattern buffer
[0-9]* - match any number of occurrences numbers in the range 0-9
[:] - match the ":" character
.* - match any number of any characters (the rest of the line)
/ - end on the match patter and beginning on the replace pattern
\1 - the first entry in the pattern buffer ( what was stored with \(...\) )
/ - end of the replace pattern
p - print
you can also try this ...
grep -n "Content-Disposition: attachment" mbox | awk -F: '{print $1}'
Or even more concisely....
sed -n '/Content-Disposition: attachment/=' file_name
Cheers
ZB
I tried all 3, and all 3 worked perfectly. The last 2 options are a whole lot easier for me to understand, even though I did read up on regular expressions, and was able to follow some of the first option.
Thanks for your help 
Sorry, I only partially read your first post. I thought there was some reason for using grep, had I read properly I would have said the same as ZB.
or maybe
awk '/Content-Disposition: attachment/ {print NR}' mbox
You can also use the below mentioned command too..
grep -n "Content-Disposition: attachment" mbox | cut -d":" -f1