Inserting a "," in a particular position of a text

user_14063423 0
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(I put a exact text and command I executed so would be looking a bit messy.)

I have a .TXT file looking like

11111111111111111111111111111111111111111111111111111111111111111111111
11111111111111111111111111111111111111111111111111111111111111111111111

And outcome I am looking for would be like

11111111111111,1111111,11,1,111,1111111111111,1,11111111,1111111111111111,111,111
11111111111111,1111111,11,1,111,1111111111111,1,11111111,1111111111111111,111,111

Command I have tried is

sed -i 's/\(.\{14\}\)\(.\{7\}\)\(.\{2\}\)\(.\{1\}\)\(.\{3\}\)\(.\{13\}\)\(.\{1\}\)\(.\{8\}\)\(.\{16\}\)\(.\{3\}\)/\1,\2,\3,\4,\5,\6,\7,\8,\9,\10,/' SOME.TXT

And outcome I have got was

11111111111111,1111111,11,1,111,1111111111111,1,11111111,1111111111111111,1111111111111110,111
11111111111111,1111111,11,1,111,1111111111111,1,11111111,1111111111111111,1111111111111110,111

I have literally no idea why these 0s suddenly popped out and ' , ' doesn't appear in the position where I command even though it worked half way.

Is this a bug or something in sed command?

sed awk regex
3 Answers

It is printing 0 in output because sed capture groups and their back-references can be up to 9 only and \10 is interpreted as \1 followed by literal 0.

You can solve it easily using FIELDWIDTHS feature of gnu-awk:

awk -v OFS=, 'BEGIN { FIELDWIDTHS = "14 7 2 1 3 13 1 8 16 3 *" } {$1 = $1} 1' file

11111111111111,1111111,11,1,111,1111111111111,1,11111111,1111111111111111,111,111
11111111111111,1111111,11,1,111,1111111111111,1,11111111,1111111111111111,111,111

Just for academic exercise, here is a working sed to solve this using 2 substitutions:

sed -E 's/(.{14})(.{7})(.{2})(.)(.{3})(.{13})(.)(.{8})(.+)/\1,\2,\3,\4,\5,\6,\7,\8,\9/; s/(.+,.{16})(.{3})(.*)/\1,\2,\3/' file
user_5482250

sed can't reference capture groups > 9, Perl can:

perl -i -pe  's/(.{14})(.{7})(.{2})(.)(.{3})(.{13})(.)(.{8})(.{16})(.{3})/$1,$2,$3,$4,$5,$6,$7,$8,$9,$10,/' SOME.TXT
user_10306750

If you insist to use sed, you can do something like:

sed 's/./&,/68;s/./&,/65;s/./&,/49;s/./&,/41;s/./&,/40;s/./&,/27;s/./&,/24;s/./&,/23;s/./&,/21;s/./&,/14' test.txt
11111111111111,1111111,11,1,111,1111111111111,1,11111111,1111111111111111,111,111
11111111111111,1111111,11,1,111,1111111111111,1,11111111,1111111111111111,111,111
user_17354060
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