grep nth line

[monkeyking]

Is there a nice unix tool to grep the nth line of a file?

thanks in advance

[thumper]

There are these wonderful inventions called pipes.

To grep the 45th line of file foo.txt for "hello"

$ head -45 foo.txt | tail -1 | grep hello

[monkeyking]

okay,
I wasn't clear enought,

I just want to "extract" the n'th line of a file.

I know I can do stuff like


head -n44 file > tmp1.file
head -n45 file > tmp2.file
diff tmp1.file tmp2.file > difference

This will give me the 45'th line but with some additional info.

[xadder]

Good old-fashioned awk is incredibly useful for these small jobs:


awk '{ if (NR==45) print $0 }' file

Or, you can pass in n as a parameter if you want to make a script:

#!/bin/bash
# Usage getn N filename

awk '{ if(NR==n) print $0 }' n=$1 $2



the syntax is a bit cryptic, but easy to learn. $0 is the whole line. $1 would be the first
column, $2 the 2nd etc.

[ghostdog74]

you can use sed


sed -n '45p' file


in awk


awk 'NR==45' file

[Mojtaba-Ebrahimi]

I have same problem priorly. there are many solution when your line number is a constant number. but if your line number saved in a variable use this one.

suppose your file name saved in a variable named File_Name and your favourite Line number saved in Line variable, then use this command:

cat -n $File_Name | grep " $Line"

now you can use cut command to cut additional information added by cat command:

cat -n $File_Name | grep " $Line" | cut -d: -f2

[DaithiF]

or just:

sed -n "${Line}p"

[geirha]

Bookmark this page http://mywiki.wooledge.org/BashFAQ, it answers alot of questions like this. For this question, number 11.

[ghostdog74]

or just:

sed -n "${Line}p"



sed -n "${Line}{p;q}"

[Chasalin]

... and what if you're grepping from a file with numeric values, you want to get line numer 7, but '7' also appears in another line? (including the leading spaces...)

I think sed or awk is the way to go and head/tail is a nice trick.


suppose your file name saved in a variable named File_Name and your favourite Line number saved in Line variable, then use this command:

cat -n $File_Name | grep " $Line"

now you can use cut command to cut additional information added by cat command:

cat -n $File_Name | grep " $Line" | cut -d: -f2

[slavik]

and this is an old thread and all solutions are available via google.