Question

我正在尝试根据MySQL语句的执行结果设置一个变量，如下所示：

    errorOut=0
    mysql -uroot -pinsite3 -rN --execute "select file_system_id from ifm.PartitionTable where physical_partition='$partName'" | while read myVal
    do
      echo "myVal = $myVal"
      if [ $myVal -eq $fsId ];then
        errorOut=1
        echo "Found equal: errorOut = $errorOut"
      fi
    done
    echo "Outside loop: errOut = $errorOut"


Here is the output:
myVal = 1
myVal = 2
Found equal: errorOut = 1
Outside loop: errOut = 0

正如你所看到的，由于管道，我无法在循环外得到变量的值（因为管道内的变量，基本上是设置了不同的过程）

有什么办法可以在循环外提取实际值吗？

Answer 1

如果您使用for...in代替read，会怎样？：

errorOut=0
for myVal in $(mysql -uroot -pinsite3 -rN --execute "select file_system_id from ifm.PartitionTable where physical_partition='$partName'")
do
  echo "myVal = $myVal"
  if [ $myVal -eq $fsId ];then
    errorOut=1
    echo "Found equal: errorOut = $errorOut"
  fi
done
echo "Outside loop: errOut = $errorOut"

Answer 2

将其写入文件，然后在循环外读取文件。

errorOut=0
errOutFile=Err$$.txt
mysql -uroot -pinsite3 -rN --execute "select file_system_id from ifm.PartitionTable where physical_partition='$partName'" | while read myVal
do
  echo "myVal = $myVal"
  if [ $myVal -eq $fsId ];then
    errorOut=1
    echo "Found equal: errorOut = $errorOut"
    echo "$errorOut" > $errOutFile
  fi
done
errorOut="$(cat $errOutFile)"

无法获得管道内设置的shell变量的准确值

2 个答案: