有群里的小伙伴說crontab里的任務不執行，具體是這樣的
*/1 * * * * /bin/date "+%Y-%m-%d %H:%M:%S" >>/data/tmp/test.log
我試了下在命令行可以執行，定時任務確實不執行，於是去翻了下日志：
#tail -f /var/spool/mail/root X-Cron-Env: <HOME=/root> X-Cron-Env: <PATH=/usr/bin:/bin> X-Cron-Env: <LOGNAME=root> X-Cron-Env: <USER=root> Message-Id: <20200108081701.8FD502100481@D3L40.localdomain> Date: Wed, 8 Jan 2020 16:17:01 +0800 (CST) /bin/sh: -c: line 0: unexpected EOF while looking for matching `"' /bin/sh: -c: line 1: syntax error: unexpected end of file From root@D3L40.localdomain Wed Jan 8 16:18:01 2020
說是語法錯誤，結尾不對，明明是兩個雙引號啊，這樣就有可能是里面有特殊字符導致命令意外中斷了，於是查了下萬能的百度發現：
The “sixth” field (the rest of the line) specifies the command to be run. The entire command portion of the line, up to a newline or % character, will be executed by /bin/sh or by the shell specified in the SHELL variable of the crontab file. Percent-signs (%) in the command, unless escaped with backslash (), will be changed into newline characters, and all data after the first % will be sent to the command as standard input. There is no way to split a single command line onto multiple lines, like the shell’s trailing “”.
大概是在crontab里%當換行符用了，想要正常使用就得加反引號\，\%這樣來用。
於是把命令改成了：
*/1 * * * * /bin/date "+\%Y-\%m-\%d \%H:\%M:\%S" >>/data/tmp/test.log
最后：
# cat test.log 2020-01-08 16:38:01 2020-01-08 16:39:01
可以了，於是想着記一下，好記性不如爛筆頭嘛。