Add a col using file name - awk

Question

I have ~ 100 files, they are a.vcf; b.vcf, d.vcf......
For example:
a.vcf
##contig= ID=chr1,length=249250621
##contig= ID=chr2,length=243199373
##contig= ID=chr3,length=198022430
##contig= ID=chr4,length=191154276
b.vcf
##contig= ID=chr5,length=180915260
##contig= ID=chr6,length=171115067
##contig= ID=chr7,length=159138663
##contig= ID=chr8,length=146364022
##contig= ID=chr9,length=141213431
##contig= ID=chr10,length=135534747
I want to add additional col as the last col, for examples, new file a_a.vcf
a_a.vcf
##contig= ID=chr1,length=249250621 a.vcf
##contig= ID=chr2,length=243199373 a.vcf
##contig= ID=chr3,length=198022430 a.vcf
##contig= ID=chr4,length=191154276 a.vcf
For single vcf file, I used the following code:
awk 'NR == 1 {print $0 " name_file"; next;}{print $0 " " FILENAME;}' a.vcf
Then I want to apply this to all the files in this folder.
for d in *.vcf; do
awk 'NR == 1 {print $0 " name_file"; next;}{print $0 " " FILENAME;}' a_$d
done
But I found the -zsh replaced $0, How could I fix the problem?
awk 'NR == 1 {print -zsh name_file; next;}{print -zsh FILENAME;}' a_a.vcf
awk 'NR == 1 {print -zsh name_file; next;}{print -zsh FILENAME;}' a_b.vcf
awk 'NR == 1 {print -zsh name_file; next;}{print -zsh FILENAME;}' a_c.vcf

Answer 1

GNU AWK is not limited to single input file, you might provide multiple files to single awk by using filenames sheared by spaces, in your case try
awk 'FNR == 1 {print $0 " name_file"; next;}{print $0 " " FILENAME;}' a.vcf b.vcf c.vcf
which should give same output as
awk 'NR == 1 {print $0 " name_file"; next;}{print $0 " " FILENAME;}' a.vcf
awk 'NR == 1 {print $0 " name_file"; next;}{print $0 " " FILENAME;}' b.vcf
awk 'NR == 1 {print $0 " name_file"; next;}{print $0 " " FILENAME;}' c.vcf
Note that I used FNR in place of NR i.e. number of line inside file rather than (global) number of line. As suggested in comments, you might further ameliorate your code exploiting OFS variable as follows
awk 'BEGIN{OFS=" "}FNR == 1 {print $0, "name_file"; next}{print $0, FILENAME}' a.vcf b.vcf c.vcf
If you want to know more about OFS and other read 8 Powerful Awk Built-in Variables – FS, OFS, RS, ORS, NR, NF, FILENAME, FNR