Remove all rows that begin with characters and keep only those that begin with numbers in Linux.

Question

[salman_96]

I have a tab sep file that looks like this. I need to prepare it so I can import it in R. The file is genome hg19 file.

1      344544     rs30540

2      284783     rs34560

14     384643     rs30567

19     584643     rs31110

Genome_phase,common=1,19,genomes=hg19
11    222643     rs30543

44    544643     rs32345

Genome_phase,common=1,23,genomes=hg19

I want to keep only the rows that start with numbers and drop all others that begin with characters. It is a huge file of a few gbs.Any way to do that in linux

Any assistance will be appreciated. Regards

Answer 1

[Alex Reynolds]

$ awk -v FS="\t" -v OFS="\t" '($1 ~ /^[0-9]/)' in.txt > out.txt

Answer 2

[cpad0112]

$ sed -n '/^[0-9]/p' test.txt
$ grep '^[0-9]' test.txt