how to insert space between individual digits in a file?

Question

My data looks like:

$ cat input
1212103122
1233321212
0000022221

I want the output to look like:

$ cat output
1 2 1 2 1 0 3 1 2 2
1 2 3 3 3 2 1 2 1 2
0 0 0 0 0 2 2 2 2 1

I tried:

sed -i 's// /g' input > output

but it does not work.

Any suggestions?

Answer 1

This worked for me:

sed 's/./& /g' input > output

$ cat input
1212103122
1233321212
0000022221

$ cat output
1 2 1 2 1 0 3 1 2 2 
1 2 3 3 3 2 1 2 1 2 
0 0 0 0 0 2 2 2 2 1 

Answer 2

Here you are:

sed 's/\(.\{1\}\)/\1 /g' input > output

And if you want to save the changes in-place:

sed -i 's/\(.\{1\}\)/\1 /g' input

How it works:

s/\(.\{1\}\)/\ /g will add a space, after each 1 character.

For instance, if you wanted an output file like:

12 12 10 31 22
12 33 32 12 12
00 00 02 22 21

You could edit my answer to:

sed -i 's/\(.\{2\}\)/\1 /g'

So it will add a space, after each 2 characters.

In addition, /\1 / is the same as /&, and will add one white-space. For instance, to add three: /\1 / or /& /. You have many more options to use. Sed is a super-powerful tool.

In addition yes, as @Law29 mentioned, this will leave a space at the end of each line if you do not remove, so to remove them while adding spaces you can add a s/ $// to the end of given solution, to do so:

sed 's/./& /g; s/ $//'

I hope this could help.

Answer 3

You have the -i option, which edits the file in place. This may have hindered you in finding the right solution.

Your problem is that you are trying to match an empty string, which sed will not allow. Instead, match any one character, and replace it with the same character followed by a space. This will leave you with a space at the end of each line, which you can remove with another sed.

$ cat input 
1212103122
1233321212
0000022221
$ sed -e 's/./& /g' -e 's/ $//' input > output
$ cat output
1 2 1 2 1 0 3 1 2 2
1 2 3 3 3 2 1 2 1 2
0 0 0 0 0 2 2 2 2 1
$ 

Answer 4

Here's an option with GNU awk:

gawk -F '' '{$1=$1}1' input > output

The principle of operation is:

• by setting an empty field separator -F '', we split the input records (lines) into individual characters¹

• by evaluating $1=$1 we force the record to be re-built with the default output field separator (which is a single space)

• 1 is true so print the result

A similar trick in perl:

perl -F'' -alne 'print join " ", @F' input > output

---

To illustrate:

$ awk -F '' '{$1=$1}1' input
1 2 1 2 1 0 3 1 2 2
1 2 3 3 3 2 1 2 1 2
0 0 0 0 0 2 2 2 2 1

---

1. see Making Each Character a Separate Field in the The GNU Awk User's Guide