Test if the first character is a number using awk -

how check if first character of string number using awk. have tried below keep getting syntax error.

awk ' { if (substr($1,1,1) == [0-9] ) print $0 }' da.txt 

i suggest use @hek2mgl solution. have pointed out of problems.

problems:

1. you should use regex inside /..regex../.
2. use ~ instead of ==.

valid:

awk '{ if (substr($1,1,1) ~ /^[0-9]/ ) print $0 }' file.txt