题解 | #打印只有一个数字的行#

awk -F "[0-9]" '{if(NF==2) print $0}' nowcoder.txt

 while read line
 do
     let count=0
     for (( i = 0; i < ${#line}; i++))
         do
             [[ ${line:i:1} =~ [0-9] ]] && ((count++))
         done
     if [ $count -eq 1 ];then
         printf "$line\n"
     fi
 done < nowcoder.txt

awk -F "" '{
    for (i = 1; i <= NF; i++) {
        if ($i ~ /[0-9]/) {
            count++
        }
    }
    if (count == 1) {
        print($0)
    }
    count = 0
}'