Alain Kelder | Insert line numbers in files painlessly with nl

Insert line numbers in files painlessly with nl

21 May 2010 coreutils, Linux Trackback

Was trying to figure out how to insert line numbers into a huge file with sed or awk, then stumbled across "nl", a sweet little baby that comes with GNU coreutils and numbering files is what it does for a living. GNU coreutils is full of gems!

Boring:

ak@gd:~$ cat file
blah
blah blah
bleh blah

Awesome:

ak@gd:~$ cat file | nl -n ln -w1 -s\|
1|blah
2|blah blah
3|bleh blah

More awesome (avoids UUOC):

ak@gd:~$ nl -n ln -w1 -s\| file
1|blah
2|blah blah
3|bleh blah

3 Comments

1. Clinton Cronin replies at 27th May 2010, 2:19 pm :

It seems to use single digits. Is there a way to let it go to double and triples?

I promptly stole and made a bash script out of this (though largely overkill) it comes in handy.
```
#!/bin/bash
file=$1
cat $file | nl -n ln -s'|'
```

2. Alain Kelder replies at 27th May 2010, 2:43 pm :

What’s up Clinton!

The syntax of “nl” seems a bit awkward, for me at least, but looks like you could do it like so:

$ cat file | nl -n rz -w3 -s\|
001|blah
002|blah
003|blah
004|blah
005|blah
006|blah
007|blah
008|blah
009|blah
010|blah
011|blah
012|blah
013|blah
014|blah
015|blah
016|blah
017|blah
018|blah
019|blah
020|blah

3. Alain Kelder replies at 27th May 2010, 2:55 pm :

Another little thing I ran into with it recently is that by default, it skips blank lines:
```
$ head -4 file | nl -n rz -w3 -s\|
001|blah
    
002|blah
003|blah
```
To number blank lines as well:
```
$ head -4 file | nl -n rz -ba -w3 -s\|
001|blah
002|
003|blah
004|blah
```

Alain Kelder is a Giant Dork

Insert line numbers in files painlessly with nl

3 Comments

Leave a comment