Numbering Array Elements - Bash Scripting

Question

I have an array named c. Its elements are filenames found in the current directory. How do I list them on their own line with a number before? For example:

1. aaa
2. filename2
3. bbb
4. asdf

The code I have now just prints each file on its own line. Like:

aaa
filename2
bbb
asdf

My code is below:

#!/bin/bash
c=( $(ls --group-directories-first $*) )

   printf '%s\n' "${c[@]}"

You asked about numbering arrays, not creating them, but the creation part deserves comment: c=( $(ls --group-directories-first $*) ) will lead to problems if any of your files have whitespace in their names. — John1024
– John1024, Commented Apr 27, 2015 at 20:13
I see that now @John1024, thanks for mentioning that. Any idea how I can fix that? — JRM1201
– JRM1201, Commented Apr 27, 2015 at 20:36
The simplest is c=( * ). This will create an array with all file names and is safe to use whatever characters are in the file names. This does approach, however, does not offer the --group-directories-first functionality. — John1024
– John1024, Commented Apr 27, 2015 at 20:41

John1024 · Accepted Answer · 2015-04-27 21:17:44Z

1

Starting with array c, here are three methods:

Using `cat -n`

The cat utility will number output lines:

$ cat -n < <(printf "%s\n" "${c[@]}")
     1  aaa
     2  filename2
     3  bbb
     4  asdf

Using `bash`

This method uses shell arithmetic to number the lines:

$ count=0; for f in "${c[@]}"; do  echo "$((++count)). $f"; done
1. aaa
2. filename2
3. bbb
4. asdf

Using `nl`

In the comments, twalberg suggests the use of nl:

$ nl < <(printf "%s\n" "${c[@]}")
     1  aaa
     2  filename2
     3  bbb
     4  asdf

The utility nl has a number of options for controlling exactly how you want the numbering done including, for example, left/right justification, inclusion of leading zeros. See man nl.

edited Apr 27, 2015 at 21:17

answered Apr 27, 2015 at 20:08

John1024

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3 Comments

twalberg Over a year ago

nl is a useful alternative to cat -n that has a number of options for controlling exactly how you want the numbering done...

JRM1201 Over a year ago

Thanks John1024, I used bash (the second method) to fix it and it worked perfectly.

John1024 Over a year ago

@twalberg, Excellent suggestion. I added nl to the answer. JRM1201, glad it worked for you.

Jahid · Accepted Answer · 2015-04-27 21:00:58Z

1

This should work:

for (( i=0; i<${#c[@]}; i++)); do
printf '%d. %s\n' $((i+1)) "${c[$i]}"
done

answered Apr 27, 2015 at 21:00

Jahid

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Using `cat -n`

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