LeetCode 194. Transpose File

awk '
{
    for (i=1; i<=NF; i++) {
        a[i] = a[i] ? a[i] " " $i : $i
    }
}
END {
    for (i=1; i<=length(a); i++) {
        print a[i]
    }
}
' file.txt

LeetCode 193. Valid Phone Numbers

grep -E "^[0-9]{3}-[0-9]{3}-[0-9]{4}$|^\([0-9]{3}\) [0-9]{3}-[0-9]{4}$" file.txt

LeetCode 192. Word Frequency

tr -s '[:space:]' '\n' < words.txt | sort | uniq -c | sort -nr | awk '{print $2, $1}'

LeetCode 195. Tenth Line

sed -n '10p' file.txt

Ubuntu 22.04 LTS Startup Service script

sudo vim /etc/systemd/system/name.service

[Unit]
Description=Description
After=network.target

[Service]
ExecStart=run ...
User=root
Group=root

[Install]
WantedBy=default.target
Alias=name.service

加上permission

sudo chmod 644 /etc/systemd/system/name.service