linux - 无法获取管道内设置的 shell 变量的准确值

Question

我正在尝试根据这样的 MySQL 语句的执行结果设置一个变量:

    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

如您所见，由于管道，我无法在循环外获取变量的值(因为管道内的变量，基本上设置为 fork 不同的进程)

有什么方法可以在循环外提取实际值吗？

Answer 1

如果像这样使用 for...in 而不是 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"