crontab用法
crontab可以定时执行某些操作，很实用。
通常Linux系统都已经自带。
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用法
$ crontab -h crontab: invalid option -- 'h' crontab: usage error: unrecognized option usage: crontab [-u user] file crontab [ -u user ] [ -i ] { -e | -l | -r } (default operation is replace, per 1003.2) -e (edit user's crontab) -l (list user's crontab) -r (delete user's crontab) -i (prompt before deleting user's crontab) -
显示当前已经添加到crontab的命令：
$ crontab -l # Edit this file to introduce tasks to be run by cron. # # Each task to run has to be defined through a single line # indicating with different fields when the task will be run # and what command to run for the task # # To define the time you can provide concrete values for # minute (m), hour (h), day of month (dom), month (mon), # and day of week (dow) or use '*' in these fields (for 'any').# # Notice that tasks will be started based on the cron's system # daemon's notion of time and timezones. # # Output of the crontab jobs (including errors) is sent through # email to the user the crontab file belongs to (unless redirected). # # For example, you can run a backup of all your user accounts # at 5 a.m every week with: # 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/ # # For more information see the manual pages of crontab(5) and cron(8) # # m h dom mon dow command * 0,12 * * * /bin/bash /home/adam/git2/sync.sh -
将默认编辑器从nano转为vim（可以直接添加到.bashrc or .zshrc中）：
export EDITOR="/usr/bin/vim" -
修改后看到参数，其含义分别是：
second/minute/hour/date of month/month/date of week/command
*表示缺省，即不考虑这个时间；如分钟为*，则说明任意分钟都可以。