标准输出的思考

test3.sh

bacth_date=$1
echo "bacth_date:$1"
echo "std_out:$?"
echo "${bacth_date}"|grep "20[0-9][0-9][0-9][0-9][0-9][0-9]"
echo "std_out:$?"
if [ $? -ne 0 ]
then
    echo "[ `date +'%Y-%M-%d'` ]" "[ERROR]" "BATCH_DATE:${bacth_date} is invalid date format ."
   echo "1"
   exit 1
fi

[centos@s202 ~]$ sh test3.sh 20191001
bacth_date:20191001
std_out:0
20191001
std_out:0


[centos@s202 ~]$ sh test3.sh 2019xxxx
bacth_date:2019xxxx
std_out:0
std_out:1

为什么第二次标准输出 1 之后 就不往下运行了

if [ $? -ne 0 ]

why?

我们继续研究：我们在第二个echo "std_out:$?"再加一个echo "std_out:$?"  去看标准输出$？变成了什么

bacth_date=$1
echo "bacth_date:$1"
echo "std_out:$?"
echo "${bacth_date}"|grep "20[0-9][0-9][0-9][0-9][0-9][0-9]"
echo "std_out:$?"
echo "std_out:$?"
if [ $? -ne 0 ]
then
    echo "[ `date +'%Y-%M-%d'` ]" "[ERROR]" "BATCH_DATE:${bacth_date} is invalid date format ."
   echo "1"
   exit 1
fi

[centos@s202 ~]$ sh test3.sh 2019xxxx
bacth_date:2019xxxx
std_out:0
std_out:1
std_out:0

结论： 运行第二个echo "std_out:$?" 又把标准输出 $？重新置值成了 0

所以 if [ $? -ne 0 ] 不成立 就不运行下面的了

 get ：echo命令的标准输出是 0

bacth_date=$1
echo "bacth_date:$1"
echo "std_out:$?"
echo "${bacth_date}"|grep "20[0-9][0-9][0-9][0-9][0-9][0-9]"
if [ $? -ne 0 ]
then
    echo "[ `date +'%Y-%M-%d'` ]" "[ERROR]" "BATCH_DATE:${bacth_date} is invalid date format ."
   echo "1"
   exit 1
fi

[centos@s202 ~]$ sh test3.sh 2019xxxx
bacth_date:2019xxxx
std_out:0
[ 2019-12-23 ] [ERROR] BATCH_DATE:2019xxxx is invalid date format .
1

OK：全部运行

代码来源：

对调度脚本日期参数检查（其实这个检查只能对非纯数字进行检查，对过长度比如20190101010101010101就无效）：

bacth_date=$1
echo "bacth_date:$1"
echo "std_out:$?"
echo "${bacth_date}"|grep "20[0-9][0-9][0-1][0-9][0-3][0-9]" >/dev/null
if [ $? -ne 0 ]
then
    echo "[ `date +'%Y-%M-%d'` ]" "[ERROR]" "BATCH_DATE:${bacth_date} is invalid date format ."
   echo "1"
   exit 1
fi

[centos@s202 ~]$ sh test3.sh 2019xxxx
bacth_date:2019xxxx
std_out:0
[ 2019-16-23 ] [ERROR] BATCH_DATE:2019xxxx is invalid date format .
1

[centos@s202 ~]$ sh test3.sh 20190101
bacth_date:20190101
std_out:0