Bash脚本手动运行,但在crontab上失败

Question

我是shell脚本的新手.我编写了一个shell脚本来对MySQL数据库进行增量备份.脚本采用可执行格式,手动执行时运行成功,但通过crontab执行时失败.

Crontab条目是这样的:

*/1 * * * * /home/db-backup/mysqlbackup.sh

下面是shell脚本代码 -

#!/bin/sh
MyUSER="root"       # USERNAME
MyPASS="password"         # PASSWORD
MyHOST="localhost"  # Hostname
Password="" #Linux Password

MYSQL="$(which mysql)"
if [ -z "$MYSQL" ]; then
echo "Error: MYSQL not found"
exit 1
fi
MYSQLADMIN="$(which mysqladmin)"
if [ -z "$MYSQLADMIN" ]; then
    echo "Error: MYSQLADMIN not found"
    exit 1
fi
CHOWN="$(which chown)"
if [ -z "$CHOWN" ]; then
    echo "Error: CHOWN not found"
    exit 1
fi
CHMOD="$(which chmod)"
if [ -z "$CHMOD" ]; then
    echo "Error: CHMOD not found"
    exit 1
fi

GZIP="$(which gzip)"
if [ -z "$GZIP" ]; then
    echo "Error: GZIP not found"
    exit 1
fi
CP="$(which cp)"
if [ -z "$CP" ]; then
    echo "Error: CP not found"
    exit 1
fi
MV="$(which mv)"
if [ -z "$MV" ]; then
    echo "Error: MV not found"
    exit 1
fi
RM="$(which rm)"
if [ -z "$RM" ]; then
    echo "Error: RM not found"
    exit 1
fi
RSYNC="$(which rsync)"
if [ -z "$RSYNC" ]; then
    echo "Error: RSYNC not found"
    exit 1
fi

MYSQLBINLOG="$(which mysqlbinlog)"
if [ -z "$MYSQLBINLOG" ]; then
    echo "Error: MYSQLBINLOG not found"
    exit 1
fi
# Get data in dd-mm-yyyy format
NOW="$(date +"%d-%m-%Y-%T")"

DEST="/home/db-backup"
mkdir $DEST/Increment_backup.$NOW
LATEST=$DEST/Increment_backup.$NOW
$MYSQLADMIN -u$MyUSER -p$MyPASS flush-logs
newestlog=`ls -d /usr/local/mysql/data/mysql-bin.?????? | sed 's/^.*\.//' | sort -g | tail -n 1`
echo $newestlog
for file in `ls /usr/local/mysql/data/mysql-bin.??????`
do
        if [ "/usr/local/mysql/data/mysql-bin.$newestlog" != "$file" ]; then
     echo $file             
     $CP "$file" $LATEST         
        fi
done
for file1 in `ls $LATEST/mysql-bin.??????`
do
 $MYSQLBINLOG $file1>$file1.$NOW.sql 
 $GZIP -9 "$file1.$NOW.sql"     
 $RM "$file1"
done
$RSYNC -avz $LATEST /home/rsync-back

• 首先,当在crontab上安排时,它没有显示任何错误.我怎样才能知道脚本是否正在运行？
• 其次,在crontab中执行shell脚本的正确方法是什么.一些博客建议改变环境变量.什么是最好的解决方案

当我回复PATH时,我得到了这个

/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/mysql/bin:/opt/android-sdk-linux/tools:/opt/android-sdk-linux/platform-tools:~/usr/lib/jvm/jdk-6/bin

Answer 1

问题可能是您的$ PATH在手动环境中与crontab运行时的不同.因此,which找不到您的可执行文件.要解决此问题,请首先在手动环境中打印路径(echo $PATH),然后在crontab中运行的脚本顶部手动设置PATH.或者只是按照完整路径参考程序.

编辑:在所有which调用之前将其添加到脚本顶部附近:

export PATH="/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/mysql/bin:/opt/android-sdk-linux/tools:/opt/android-sdk-linux/platform-tools:~/usr/lib/jvm/jdk-6/bin"

Answer 2

另一种更通用的方法是让cron运行用户的bash登录过程.除了PATH之外,这还将获取任何LD_LIBRARY_PATH,LANG设置,其他环境变量等.为此,请将您的crontab条目编码为:

34  12  * * *   bash -l /home/db-backup/mysqlbackup.sh

Answer 3

我的问题是我在/etc/cron.d（Centos 7）中设置了cron作业。似乎这样做时，我需要指定执行脚本的用户，这与在用户级别输入cronjob不同。

我要做的就是

*/1 * * * * root perl /path/to/my/script.sh
*/5 * * * * root php /path/to/my/script.php

其中“ root”表示我以root用户身份运行脚本。还需要确保在文件顶部定义了以下内容。您的路径可能不同。如果不确定，请尝试使用命令“哪个perl”，“哪个php”。

SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin