I have a file with a list of values that end with a letter. Is there an easy way to add a space or tab before the last character of each line to separate the number from the letter?


So that the output looks like this:

44 A  
354 T  
1453 C  
77 D

If you never have any white space after the last character and before the end of the line, use:

sed 's/.$/ &/' file


perl -pe 's/.$/ $&/' file

If you can have whitespace before the end of the line, use this instead:

perl -pe 's/(.*)(\S)/$1 $2/' file
  • Nice. Also s/(?=\S\s+$)/ / but I don't think that gains anything over your sol'n – glenn jackman Oct 7 '15 at 19:47

This works for the stated case:

sed 's/\(.\)$/\ \1/' file.txt 

It will break down if you want a space anywhere else.


if lines are not empty...

perl -pe 'substr($_,-2,0)=" "'

In vi, you can do it with:

:%s/\(.\)$/ \1/

Broken down, this is:

:%s    #Apply substitution to all lines
   /\(.\)$    #Search for a single character followed by the end of the line
          / \1/    #Replace with a space followed by that character

This does assume you don't have any whitespace at the end of your lines. If that's not always the case, use:

:%s/\(\S\)\s*$/ \1/

This will strip off any trailing whitespace and add a single space before the last remaining character on each line.

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