Awk-sed help : to remove first and last line with pattern match:

Shell Programming and Scripting
1

awk , sed Experts,

I want to remove first and last line after pattern match "vg" :
I am trying : # sed '1d;$d' works fine , but where the last line is not having vg entry it is deleting one line of data.

  • So it should check for the pattern vg if present , then it should delete the line , else do nothing.

file1 :

/dev/vgP2XT
/dev/disk/disk4415
/dev/disk/disk4335
/dev/disk/disk4214
/dev/disk/disk4413
/dev/disk/disk4423
/dev/disk/disk41313
/dev/disk/disk21063
/dev/disk/disk20702
/dev/disk/disk21423
/dev/disk/disk21122
/dev/vgQ4XT

I have tried: the above sed on the file2 , but cutting one data line, that I don't want in the output :

file2 :

/dev/vgP2XT
/dev/disk/disk4415
/dev/disk/disk4335
/dev/disk/disk4214
/dev/disk/disk4413
/dev/disk/disk4423
/dev/disk/disk41313
/dev/disk/disk21063
/dev/disk/disk20702
/dev/disk/disk21423
/dev/disk/disk21122

Tried:
sed '1d;$d' , but it is deleting last line "disk21122"
How to tell sed to check for the pattern, and then delete, if possible.

So I want the output should be:

/dev/disk/disk4415
/dev/disk/disk4335
/dev/disk/disk4214
/dev/disk/disk4413
/dev/disk/disk4423
/dev/disk/disk41313
/dev/disk/disk21063
/dev/disk/disk20702
/dev/disk/disk21423
/dev/disk/disk21122

Thanks,

2

Try:

grep '/dev/d'

grep -v '/dev/vg'

--
or, if it needs to be only on the 1st and the last line:

sed '1{\|/dev/vg|d;}; ${//d;}' infile
1 Like
3

Hi Scrutinizer ,
Thanks, but the sed did not work well,
please advise, how not to print, first and last line if pattern matches to the first and last line.

# cat infile
/dev/vgP2XT
/dev/disk/disk4415
/dev/disk/disk4335
/dev/disk/disk4214
/dev/disk/disk4413
/dev/disk/disk4423
/dev/disk/disk41313
/dev/disk/disk21063
/dev/disk/disk20702
/dev/disk/disk21423
/dev/disk/disk21122
/dev/vgQ4XT

# sed '1{\|/dev/vg|d;}; ${//d;}' infile   
/dev/disk/disk4415
/dev/disk/disk4335
/dev/disk/disk4214
/dev/disk/disk4413
/dev/disk/disk4423
/dev/disk/disk41313
/dev/disk/disk21063
/dev/disk/disk20702
/dev/disk/disk21423
/dev/disk/disk21122
/dev/vgQ4XT
#

It did not removed the last "vg" pattern matched entry. /dev/vgQ4XT

4

Try this instead:

sed '\|/dev/vg|{1d; $d;}' infile
1 Like
5

Thanks Scrutinizer, this works great .

sed '\|/dev/vg|{1d; $d;}' infile

I am not able to understand why "| | " used in between ,
Could please explain , Thanks again.

6

Hi revri, \| .. | is the same as / .. / , the difference is that the / characters in /dev/vg would need to be escaped:

sed '/\/dev\/vg/{1d; $d;}' infile

You can use most characters as long as the first one is escaped:

sed '\:/dev/vg:{1d; $d;}' infile