awk

awk '{
	if ($0 ~ /\[23\/Apr\/2020:2[0-2]/) {
         a[$1]=1
     } 
} END {
     print (length(a))
 }'

使用grep

grep "23/Apr/2020" | cut -c '-12' | sort -u | wc -l

使用 shell

declare -A map
while read line
    do
        a=($line)
        [[ ${a[3]} =~ 23/Apr/2020:2[0-2] ]] && ((map["${a[0]}"]=0))
    done < nowcoder.txt
printf "${#map[*]}"