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从 shell 脚本配置 cron

tag-icon • tag-icon bash shell-script shell cron
从 shell 脚本配置 cron

我有一个包含以下几行的 shell 脚本（完整脚本位于帖子末尾）：

CRON_BCK_CMD=/home/user/bck.sh
CRON_CONF=" */30 * *   *   *     $CRON_BCK_CMD"

但是当我简单地在 shell 中运行这些然后echo $CRON_CONF 我得到

*/30 ... /home/user/bck.sh

其中...代表 /home/user 列出的所有文件，例如*/30 bck.sh bck-ssh.sh Documents davmail.log.../home/user/bck.sh

我认为该脚本曾经在我的另一台机器上运行过。我该如何做我明显想做的事情？

# SETUP
# CRON_BCK_CMD sets the full path to the backup script
CRON_BCK_CMD=/home/user/bck.sh
# CRON_CONF sets the configuration line for cron, the time is set as:
# minute hour day_of_month month day_of_week
# * means any value, eg. 15 * * * * would mean backup at any hour, any day, when minute on the clock equals 15
# repetition can be managet by /, eg. */15 * * * * means backup every 15 minutes
CRON_CONF=" */30 * *   *   *     $CRON_BCK_CMD"
# SETUP END
CRON_IS_BCK_CMD=$(crontab -l 2>/dev/null | grep $CRON_BCK_CMD) || true
if [[ ! $CRON_IS_BCK_CMD ]]
then
    echo "No entry for backup found in crontab, do you want to schedule?"
    read -p "y/n (y) " REPLY
    if [[ $REPLY =~ ^[n|N]$ ]]
    then
        echo "Nothing to do, exitting..."
        exit 0
    fi
    (crontab -l ; echo "$CRON_CONF") | crontab -
else
    echo "Found crontab entry, do you want to stop schedule?"
    read -p "y/n (y) " REPLY
    if [[ $REPLY =~ ^[n|N]$ ]]
    then
        echo "Nothing to do, exitting..."
        exit 0
    fi
    crontab -l | grep -v $CRON_BCK_CMD | crontab -
fi

答案1

使用引号将变量表示为字符串，而不是变量的原始来源。因为否则，如果星号跟在斜杠后面，则在目录路径规范中将被视为“星号约定” - 因此星号将代表指定目录中的所有文件。

如果您想通过 CRON 运行 shell 脚本，对于某些情况下的问题，还建议通过 shell 解释器 ( /bin/bash -c /home/script.sh &) 运行脚本，并在后台将其作为任务运行（&最后）。

#!/bin/bash

# SETUP
# CRON_BCK_CMD sets the full path to the backup script
CRON_BCK_CMD="/home/user/bck.sh"
# CRON_CONF sets the configuration line for cron, the time is set as:
# minute hour day_of_month month day_of_week
# * means any value, eg. 15 * * * * would mean backup at any hour, any day, when minute on the clock equals 15
# repetition can be managet by /, eg. */15 * * * * means backup every 15 minutes
CRON_CONF="*/30 * * * *      /bin/bash -c $CRON_BCK_CMD &"     # change the Shell to the one used in your Linux (dash, sh, ash, ...)
# SETUP END

if crontab -l | grep "$CRON_BCK_CMD" > /dev/null; then
    echo "Found crontab entry, do you want to stop schedule?"
    read -p "y/n (y): " REPLY
    if [ "$REPLY" != "n" ]; then            # if the "ENTER" key was pressed or the "y" character was typed...
        crontab -l | grep -v "$CRON_BCK_CMD" | crontab -
    fi
else
    echo "No entry for backup found in crontab, do you want to schedule?"
    read -p "y/n (y): " REPLY
    if [ "$REPLY" != "n" ]; then            # if the "ENTER" key was pressed or the "y" character was typed...
        (crontab -l; echo "$CRON_CONF") | crontab -
    fi
fi

exit 0

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