add header to columns from list text file awk - linux

Question

I have a very large text file with hundreds of columns. I want to add a header to every column from an independent text file containing a list.
My large file looks like this:
largefile.txt
chrom start end 0 1 0 1 0 0 0 etc
chrom start end 0 0 0 0 1 1 1 etc
chrom start end 0 0 0 1 1 1 1 etc
my list of headers:
headers.txt
h1
h2
h3
wanted output:
output.txt
h1 h2 h3 h4 h5 h6 h7 etc..
chrom start end 0 1 0 1 0 0 0 etc
chrom start end 0 0 0 0 1 1 1 etc
chrom start end 0 0 0 1 1 1 1 etc

Answer 1

$ awk 'NR==FNR{h=h OFS $0; next} FNR==1{print OFS OFS h} 1' head large | column -s ' ' -t
h1 h2 h3
chrom start end 0 1 0 1 0 0 0 etc
chrom start end 0 0 0 0 1 1 1 etc
chrom start end 0 0 0 1 1 1 1 etc
or if you prefer:
$ awk -v OFS='\t' 'NR==FNR{h=h OFS $0; next} FNR==1{print OFS OFS h} {$1=$1}1' head large
h1 h2 h3
chrom start end 0 1 0 1 0 0 0 etc
chrom start end 0 0 0 0 1 1 1 etc
chrom start end 0 0 0 1 1 1 1 etc

Answer 2

Well, here's one. OFS is tab for eye candy. From the OP I concluded that the headers should start from the fourth field, hence +3s in the code.
$ awk -v OFS="\t" ' # tab OFS
NR==FNR { a[NR]=$1; n=NR; next } # has headers
FNR==1 { # print headers in the beginning of 2nd file
$1=$1 # rebuild record for tabs
b=$0 # buffer record
$0="" # clear record
for(i=1;i<=n;i++) # spread head to fields
$(i+3)=a[i]
print $0 ORS b # output head and buffered first record
}
{ $1=$1 }1' head data # implicit print with record rebuild
h1 h2 h3
chrom start end 0 1 0 1 0 0 0 etc
chrom start end 0 0 0 0 1 1 1 etc
chrom start end 0 0 0 1 1 1 1 etc
Then again, this would also do the trick:
$ awk 'NR==FNR{h=h (NR==1?"":OFS) $0;next}FNR==1{print OFS OFS OFS h}1' head date
h1 h2 h3
chrom start end 0 1 0 1 0 0 0 etc
chrom start end 0 0 0 0 1 1 1 etc
chrom start end 0 0 0 1 1 1 1 etc

Answer 3

Use paste to pivot the headers into a single line and then cat them together with the main file (- instead of a file name means stdin to cat):
$ paste -s -d' ' headers.txt | cat - largefile.txt
If you really need the headers to line up as in your example output you can preprocess (either manually or with a command) the headers file, or you can finish with sed (for just one option) as below:
$ paste -s -d' ' headers.txt | cat - largefile.txt | sed '1 s/^/ /'
h1 h2 h3
chrom start end 0 1 0 1 0 0 0 etc
chrom start end 0 0 0 0 1 1 1 etc
chrom start end 0 0 0 1 1 1 1 etc