awk '{
l=length($0)
f=l%3
for (i=1;i<=l;i++){
printf substr($0,i,1)
if((i-f)%3==0 && i!=l)
printf ","
}
print ""
}' nowcoder.txt
awk '{
l=length($0)
f=l%3
for (i=1;i<=l;i++){
printf substr($0,i,1)
if((i-f)%3==0 && i!=l)
printf ","
}
print ""
}' nowcoder.txt