linux - 如果已经存在，如何避免设置 cron

Question

我正在使用以下命令设置一个 cron

crontab -l | { 猫; echo -e "#Adding cron task to execute imz script\n0 */1 * * */usr/local/sbin/generate_imz_report.sh"; } |定时任务-

通过 shell 脚本。每次我执行脚本时，它都会为此脚本添加一个新条目

xyx.local: ~ # crontab -l
#Adding cron task to execute imz script
0 */1 * * * /usr/local/sbin/generate_imz_report.sh
#Adding cron task to execute imz script
0 */1 * * * /usr/local/sbin/generate_imz_report.sh
#Adding cron task to execute imz script
0 */1 * * * /usr/local/sbin/generate_imz_report.sh
#Adding cron task to execute imz script
0 */1 * * * /usr/local/sbin/generate_imz_report.sh
#Adding cron task to execute imz script
0 */1 * * * /usr/local/sbin/generate_imz_report.sh
#Adding cron task to execute imz script
0 */1 * * * /usr/local/sbin/generate_imz_report.sh

为了避免这种情况，我尝试了以下方法

grep '#Adding cron task to execute imz script'/etc/crontab ||定时任务-l | { 猫; echo -e "#Adding cron task to execute imz script\n0 */1 * * */usr/local/sbin/generate_imz_report.sh"; } |定时任务-

但这行不通。如果已存在于 shell 脚本中，如何避免添加 cron 条目？

Answer 1

如果要添加的 cron 作业已经存在，则需要检查 cron 文件

SCRIPT="generate_imz_report.sh"
if crontab -l | grep $SCRIPT > /dev/null ; then
    echo "Cron job already installed."
else
    crontab -l > newcronjobs                                       # Write out old crontab
    echo "0 */1 * * * /usr/local/sbin/$SCRIPT" >> newcronjobs      # Append new cron job into cron file
    crontab newcronjobs                                            # Install new cron file
    rm newcronjobs
    echo "New cron job is added to crontab!!"
fi