Using awk and sed

[SAM_24]

Hi,

Using either awk and sed I want to acheive this:

When I search for line 2 I want to print line1

line1
line2

How to do it?

Using GNU grep I can acheive it. But I want to use either sed or awk or both.

Thanks.

[Leif Halvarsson_2]

Hi
I am not sure I understand exact what you want to do but in general awk will be a good tool for such job. Here is a example, perhaps this can give you an idea. The example is from the "real world" but I have simplified it here.

I have a file with a long list of information about backup tapes and want the media id of all tapes which is not protected. The second field of the first line contains the id and the second fild of the second line protected or not.

The file:

Mediumidentifier 0901:3cf68aa3:55a6:0001
Protected Permanent

Mediumidentifier 0901:3cf68aa3:55a6:0002
Protected None



The awk script:

$1 == "Mediumidentifier" { IDE = $2}
$1 == "Protected" { if ($2 == "None") print IDE }

The script reads the file, line for line, if the first field is "Mediumidentifier" it load the variable IDE whith the second field of this line.
When it reads the next line and find the first field is "Protected" it check the second fild for "None". If so it print out the variable IDE.
As "Mediumidentifier" appers in the file before "Protected" the id of the not protected medium will pe printed.

Hope this can help you.

[James R. Ferguson · Accepted solution]

Hi Raj:

# awk '{if ($2~/JKL/) {print X;B=1} else X=$0;B=0};END {if (B==1) print X}' /tmp/input

Given /tmp/input like:

1 ABC
2 DEF
3 GHI
4 JKL
5 MNO
6 PQR
7 STU

...will print

3 GHI

Regards!

...JRF...

[H.Merijn Brand (procura]

perl -ne '/line2/&&print $p,$_;$p=$_' infile

[Fred Martin_1]

This is how I usually do that, with awk:

awk '
BEGIN{last="null"}
/searchstr/{print last}
last=$0
' filename

searchstr = the search string
filename = the file you're working on

Basically it just copies each new line into the variable "last" ... so if you find a match for searchstr, "last" holds the last line that was read.

The BEGIN statement pre-loads the "last" variable in case you get a match for searchstr on the very first line.

Fred