Routine scheduling of crontab in Linux

In Linux, crontab is used for routine work arrangements. 1. What is crontab? Periodic daemon processes for handling To-Do items and plans for dead tasks. 2. crontab command parsing. Example: 0 0 ** 1-5 cd/home/hiperry ;. /shutDwon. sh>. /logs/shutDwon. log 2> & 1 -- execute the custom shutdown script at every night and write the log information to the specified log file. Command Parsing :#. ---------------- minute (0-59) # |. ------------- hour (0-23) # |. ---------- which day of the month (1-31) # |. ------- month (1-12) OR jan, feb, mar, apr... # |. ---- day of the week (0-6) (Sunday = 0 or 7) OR sun, mon, tue, wed, thu, fri, sat # | # *** command to be executed> indicates the redirection location. For example, echo "123">/home/123.txt 1 indicates stdout standard output, the default value of the system is 1, so ">/dev/null" is equivalent to "1>/dev/null" 2 indicates stderr standard error & indicates equivalent meaning, 2> & 1, 2 is equivalent to 12> & 1 indicates that all standard output and error output will be redirected to an out. file 3. common crontab operations: crontab file: crontab-l edit crontab file: crontab-e Delete crontab file: crontab-r