how to add a row name column into a file in linux?

Question

I Have a huge file (50000 rows) looks like :

input.txt:

123315334262625363534
265343426272282827262
224343536625242536363
635352627273635373732
363353533637383838327
635342422325337474524

I want to add row numbers as the first column at the beginning of the file while each number repeated two times:

1 123315334262625363534
1 265343426272282827262
2 224343536625242536363
2 635352627273635373732
3 363353533637383838327
3 635342422325337474524

any suggestion please?

cuonglm · Accepted Answer · 2015-10-05 18:53:25Z

1

With awk:

awk '{getline l; printf "%d %s\n%d %s\n", ++i, $0, i, l}' <in >out

answered Oct 5, 2015 at 18:53

cuonglm

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Costas · Accepted Answer · 2015-10-05 19:50:29Z

0

Other awk

awk '{print ++count, $0}NR%2{count--}' <in >out

sed + nl

sed 'N;s/\n/@/' <in |
nl |
sed 's/\(\(^\s*[0-9]*\s*\).*\)@/\1\n\2/' >out

answered Oct 5, 2015 at 19:50

Costas

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JJoao · Accepted Answer · 2015-10-05 22:15:37Z

0

perl -pe 'printf "%d ", .5+$./2'

answered Oct 5, 2015 at 22:15

JJoao

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3 Answers 3