How can I add numbers to the beginning of every line in a file?
E.g.:
This is the text from the file.
Becomes:
000000001 This is 000000002 the text 000000003 from the file.
Asked
Active
Viewed 4.8k times
64
7 Answers
124
Don't use cat or any other tool which is not designed to do that. Use the program:
nl - number lines of files
Example:
$ nl --number-format=rz --number-width=9 foobar
$ nl -n rz -w 9 foobar # short-hand
Because nl is made for it ;-)
-
7`ls | nl #nl for dummies` – Aaron Blenkush Sep 09 '15 at 05:45
-
nl doesn't really help in all scenarios. see below: $ cat test123 123 sd $ nl test123 1 123 2 sd $ awk '{print NR,$0}' test123 1 123 2 3 sd – egorulz Mar 21 '16 at 15:15
-
2It doesn't output the lines until EOF is read. So you can't use it to number output of a long-running program on-line. – arekolek Sep 11 '16 at 18:26
-
2@egorulz Use `-ba` switch. – Hynek -Pichi- Vychodil Nov 29 '16 at 11:41
39
AWK's printf, NR and $0 make it easy to have precise and flexible control over the formatting:
~ $ awk '{printf("%010d %s\n", NR, $0)}' example.txt
0000000001 This is
0000000002 the text
0000000003 from the file.
Raymond Hettinger
- 216,523
- 63
- 388
- 485
-
Wonderful! I needed this to populate a huge array of static int declarations, so I had something like `public static final int CONSTANTX;` and I wanted something like `public static final int CONSTANTX;=X` where `X` is the number of the line in the source file. I rearranged your answer as `awk '{printf("%s = %d;\n", $0, NR-4)}' Constants.java` and it worked like a charm! – afe Jan 16 '19 at 13:20
32
You're looking for the nl(1) command:
$ nl -nrz -w9 /etc/passwd
000000001 root:x:0:0:root:/root:/bin/bash
000000002 daemon:x:1:1:daemon:/usr/sbin:/bin/sh
000000003 bin:x:2:2:bin:/bin:/bin/sh
...
-w9 asks for numbers nine digits long; -nrz asks for the numbers to be formatted right-justified with zero padding.
sarnold
- 102,305
- 22
- 181
- 238
-
That's the exact answer and a good one, but for a homework style question it may have been better to offer a hint, a link, or a more general purpose solution. – Raymond Hettinger Nov 21 '11 at 01:45
-
3@Raymond, true enough, but I've not seen any indication that this is homework. Simple? Sure. But there's a giant pile of text-processing utilities on these things that even experienced developers never learn about. – sarnold Nov 21 '11 at 01:47
-
@Raymond: I suggest undeleting your answer, I like it. Different tools might excel for different reasons, and `awk(1)` certainly excels at tasks like this. – sarnold Nov 21 '11 at 01:48
-
I only knew because I fell for the a previous question a few minutes ago: http://stackoverflow.com/questions/8206280/delete-all-lines-beginning-with-a-from-a-file Also, the unusual number of leading zeros in the example was another hint :-) – Raymond Hettinger Nov 21 '11 at 01:49
-
1This is not for homework. I just thought, it could take me 2 hours to figure out how to do that in `awk`, using some for loop, which would take another 30 minutes for the script to run through the file; or I could ask here. I've never heard of `nl` before. Am I posting the wrong kind of questions? – Village Nov 21 '11 at 02:08
-
4Village: not at all -- Stack Overflow is intended to answer questions of all levels. @Raymond just noticed that you've got three questions asked in a short time frame asking for solutions to problems similar to homework a professor might assign in a "Learning Unix" course. One alone sounds like someone looking for a solution to a problem, but all three taken together makes us wonder if we're doing your homework for you. :) – sarnold Nov 21 '11 at 02:18
17
cat -n thefile will do the job, albeit with the numbers in a slightly different format.
8
Easiest, simplest option is
awk '{print NR,$0}' file
See comment above on why nl isn't really the best option.
egorulz
- 1,455
- 2
- 17
- 28
6
Here's a bash script that will do this also:
#!/bin/bash
counter=0
filename=$1
while read -r line
do
printf "%010d %s" $counter $line
let counter=$counter+1
done < "$filename"
slashdottir
- 7,835
- 7
- 55
- 71
