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多次尝试该命令

tag-icon • tag-icon shell shell-scripting scripting
多次尝试该命令

我需要执行一个命令并检查它是否成功。如果出现错误，我应该再试一次，并且以下代码按预期工作。

但是如果我需要尝试相同的命令 3 或 4 次才能成功执行怎么办？ if / else 子句将变得非常复杂。

some command

if [ $? -eq 0 ];then
echo "success"
else 

echo "failed first attempt trying again"

some command

if [ $? -eq 0 ];then
echo "success in second attempt"
else
echo "failed second attempt"
fi

fi

有没有更好的方法来编写一个脚本，在退出之前尝试该命令四次？

答案1

使用循环执行 /usr/local/some/command 的次数由 MAX_TRIES 决定。如果所有执行尝试均未成功，则会出错并显示代码 $ERR。如果成功，则会立即退出 0 并跳出循环。

#!/bin/bash

ERR=1 # or some non zero error number you want
MAX_TRIES=4 
COUNT=0
while [  $COUNT -lt $MAX_TRIES ]; do
   /usr/local/some/command
   if [ $? -eq 0 ];then
      exit 0
   fi
   let COUNT=COUNT+1
done
echo "Too many non-successful tries"
exit $ERR

如果你愿意，你可以使用 ac 风格的循环

 #!/bin/bash
 ERR=1 # or some non zero error number you want
 MAX_TRIES=4

 for (( i=1; i<=$MAX_TRIES; i++ ))
   do
     /usr/local/some/command
     if [ $? -eq 0 ];then
        exit 0
     fi
   done
echo "Too many non-sucessful tries"
exit $ERR

答案2

我真的很奇怪你怎么不知道关于 while 循环。

编辑。按照友好版主的要求，插入，重大的 狂欢蛋糕。耶，蛋糕！

while [ $w_count -lt $w_maxtries ]; do
   some command
   if [ $? -ne 0 ]; then
      # cmd failed
      let w_count=w_count+1
      # optional, consider redirecting to STDERR.
      echo "Warning, command failed the ${w_count}th time!"
      if [[ $w_count -ge $(( $w_maxtries - 1 )) ]]; then
        # whoops too many tries
        echo "Giving up"
        exit 1
      fi
   else
      # Yay it worked
      break
   fi
done
# continue here.

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