Shell Script To Number Lines Of Files

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Q. How do I number each line of a text file? How do I write a shell script to display text file with line numbers added?

A. You don’t have to write a shell script to add numbers to text file or code sample. You can use nl command which write each FILE to screen with line numbers added.


nl command example

Type the command as follows:
$ nl /etc/passwd
Sample output:

     1  root:x:0:0:root:/root:/bin/bash
     2  daemon:x:1:1:daemon:/usr/sbin:/bin/sh
     3  bin:x:2:2:bin:/bin:/bin/sh
     4  sys:x:3:3:sys:/dev:/bin/sh
     5  sync:x:4:65534:sync:/bin:/bin/sync
     6  games:x:5:60:games:/usr/games:/bin/sh
     7  man:x:6:12:man:/var/cache/man:/bin/sh
     8  lp:x:7:7:lp:/var/spool/lpd:/bin/sh
     9  mail:x:8:8:mail:/var/mail:/bin/sh
    10  news:x:9:9:news:/var/spool/news:/bin/sh
    40  quagga:x:119:126:Quagga routing suite,,,:/var/run/quagga/:/bin/false
    41  oracle:x:1004:1004::/usr/lib/oracle/xe:/bin/bash
    42  telnetd:x:112:120::/nonexistent:/bin/false

nl command has few more options:
$ nl --help

Usage: nl [OPTION]... [FILE]...
Write each FILE to standard output, with line numbers added.
With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
  -b, --body-numbering=STYLE      use STYLE for numbering body lines
  -d, --section-delimiter=CC      use CC for separating logical pages
  -f, --footer-numbering=STYLE    use STYLE for numbering footer lines
  -h, --header-numbering=STYLE    use STYLE for numbering header lines
  -i, --page-increment=NUMBER     line number increment at each line
  -l, --join-blank-lines=NUMBER   group of NUMBER empty lines counted as one
  -n, --number-format=FORMAT      insert line numbers according to FORMAT
  -p, --no-renumber               do not reset line numbers at logical pages
  -s, --number-separator=STRING   add STRING after (possible) line number
  -v, --first-page=NUMBER         first line number on each logical page
  -w, --number-width=NUMBER       use NUMBER columns for line numbers
      --help     display this help and exit
      --version  output version information and exit

By default, selects -v1 -i1 -l1 -sTAB -w6 -nrn -hn -bt -fn.  CC are
two delimiter characters for separating logical pages, a missing
second character implies :.  Type \\ for \.  STYLE is one of:

  a         number all lines
  t         number only nonempty lines
  n         number no lines
  pBRE      number only lines that contain a match for the basic regular
              expression, BRE

FORMAT is one of:

  ln   left justified, no leading zeros
  rn   right justified, no leading zeros
  rz   right justified, leading zeros


Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

12 comment

  1. Hello, I’m new in linux, please help me to write this shell script and explain them
    1- Write a shell script ( that :
    – Take as command-line options any number of text files
    -Read in each of these files, converts all the letters to uppercase, and then stores the results in a file of the same name but with a .caps extension

    2- Write a script ( that will take a single filename as an argument and adds execute permission to the file for the user, but only if the file is a regular file.
    Your script must check to see that there is exactly one argument. If there are no arguments or more than one arguments, your script must produce a “usage” message that tells how to use the script.

  2. How would you connect from one UNIX terminal to another using SSH can any one explain with example.

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