sed backreference: get each line and append it to end of line

Question

I have a file with following content:

$ cat -n w
     1  Smith   John    12345   jsmith
     2  Jones   Robert  23456   rjones
     3  Green   Ralph   34567   rgreen
     4  Brown   Fred    45678   fbrown
     5  Orange  Mabel   56789   morang

I want to get each line and then append at the end of that line the same text of that line.

Example I want this output:

$ cat -n w
     1  Smith   John    12345   jsmith  Smith   John    12345   jsmith
     2  Jones   Robert  23456   rjones  Jones   Robert  23456   rjones
     3  Green   Ralph   34567   rgreen  Green   Ralph   34567   rgreen
     4  Brown   Fred    45678   fbrown  Brown   Fred    45678   fbrown
     5  Orange  Mabel   56789   morange Orange  Mabel   56789   morange

I looked into sed command with backreferencing however I can't get it to work

$ sed 's/(.*)/\t\1/' wider
sed: -e expression #1, char 12: invalid reference \1 on `s' command's RHS

Answer 1

sed use BRE by default, you need to escape \(...\) to capture the matching:

LC_ALL=C sed 's/\(.*\)/\1\t\1/' <file

or using -E to enable ERE (which available in GNU sed and BSD sed, and will become standard soon), so you must not escape (...):

LC_ALL=C sed -E 's/(.*)/\1\t\1/' <file

Setting locale to C help you match invalid unicode characters.

But, it's better job for paste:

paste file file

or awk:

awk '{printf "%s\t%s\n", $0, $0}' <file

Answer 2

Try this:

sed 's/\(.*\)/\1\t\1/' <filename>

Answer 3

if you don't have anything against using awk, here is a way to do it :

awk '{print $0"\t"$0}'