bash - Add index column to CSV file -

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i have large comma-separated file (6gb) , add index column it. i'm looking @ unix type solutions efficiency. i'm using mac.

i have this:

v1  v2  v3 0.4625  0.9179  0.8384 0.9324  0.2486  0.1114  0.6691  0.7813  0.6705 0.1935  0.3303  0.4336

would this:

id  v1  v2  v3 1   0.4625  0.9179  0.8384 2   0.9324  0.2486  0.1114 3   0.6691  0.7813  0.6705 4   0.1935  0.3303  0.4336

this work:

awk -f'\t' -v ofs='\t' '   nr == 1 {print "id", $0; next}   {print (nr-1), $0} ' input.csv > output.csv

in awk, nr variable "the total number of input records seen far", in general means "the current line number". nr == 1 in first line how match first record , add "id" column header, , remaining lines use nr-1 index.

the -f'\t' argument sets input field separator, , -vofs='\t' sets output field separator.


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