如何运行 bash 命令直到成功或超时？

Question

如何重试 bash 命令，直到其状态正常或达到超时？

我最好的镜头（我正在寻找更简单的东西）：

NEXT_WAIT_TIME=0
COMMAND_STATUS=1
until [ $COMMAND_STATUS -eq 0 || $NEXT_WAIT_TIME -eq 4 ]; do
  command
  COMMAND_STATUS=$?
  sleep $NEXT_WAIT_TIME
  let NEXT_WAIT_TIME=NEXT_WAIT_TIME+1
done

Answer 1

您可以通过将

command

放在测试中并以不同的方式进行增量来稍微简化事情。否则脚本看起来不错：

NEXT_WAIT_TIME=0
until (( NEXT_WAIT_TIME == 5 )) || cmd; do
    sleep "$(( NEXT_WAIT_TIME++ ))"
done
(( NEXT_WAIT_TIME < 5 ))

Answer 2

一行最短，也许是最好的方法：

timeout 12h bash -c 'until ssh root@mynewvm; do sleep 10; done'

由 http://jeromebelleman.gitlab.io/posts/devops/until/

提供

Answer 3

重试功能

此脚本可以从 retrying-commands-in-shell-scripts

下载

#!/bin/bash
     
# Retries a command on failure.
# $1 - the max number of attempts
# $2... - the command to run
retry() {
   local -r -i max_attempts="$1"; shift
   local -r cmd="$@"
   local -i attempt_num=1
  
   until $cmd
      do
         if (( attempt_num == max_attempts ))
         then
            echo "Attempt $attempt_num failed and there are no more attempts left!"
            return 1
         else
            echo "Attempt $attempt_num failed! Trying again in $attempt_num seconds..."
            sleep $(( attempt_num++ ))
         fi
   done
}

• 用法示例：

  retry 5 ls -ltr foo
  

• 如果您想重试脚本中的某个函数，请按如下所示使用它：

   # example usage:
   foo()
   {
      #whatever you want do.
   }

   declare -fxr foo
   retry 3 timeout 60 bash -ce 'foo'

Answer 4

组装一些工具。

重试：https://github.com/kadwanev/retry

超时：http://manpages.courier-mta.org/htmlman1/timeout.1.html

那就看看神奇吧

retry timeout 3 ping google.com

PING google.com (173.194.123.97): 56 data bytes
64 bytes from 173.194.123.97: icmp_seq=0 ttl=55 time=13.982 ms
64 bytes from 173.194.123.97: icmp_seq=1 ttl=55 time=44.857 ms
64 bytes from 173.194.123.97: icmp_seq=2 ttl=55 time=64.187 ms
Before retry #1: sleeping 0.3 seconds
PING google.com (173.194.123.103): 56 data bytes
64 bytes from 173.194.123.103: icmp_seq=0 ttl=55 time=56.549 ms
64 bytes from 173.194.123.103: icmp_seq=1 ttl=55 time=60.220 ms
64 bytes from 173.194.123.103: icmp_seq=2 ttl=55 time=8.872 ms
Before retry #2: sleeping 0.6 seconds
PING google.com (173.194.123.103): 56 data bytes
64 bytes from 173.194.123.103: icmp_seq=0 ttl=55 time=25.819 ms
64 bytes from 173.194.123.103: icmp_seq=1 ttl=55 time=16.382 ms
64 bytes from 173.194.123.103: icmp_seq=2 ttl=55 time=3.224 ms
Before retry #3: sleeping 1.2 seconds
PING google.com (173.194.123.103): 56 data bytes
64 bytes from 173.194.123.103: icmp_seq=0 ttl=55 time=58.438 ms
64 bytes from 173.194.123.103: icmp_seq=1 ttl=55 time=94.828 ms
64 bytes from 173.194.123.103: icmp_seq=2 ttl=55 time=61.075 ms
Before retry #4: sleeping 2.4 seconds
PING google.com (173.194.123.103): 56 data bytes
64 bytes from 173.194.123.103: icmp_seq=0 ttl=55 time=43.361 ms
64 bytes from 173.194.123.103: icmp_seq=1 ttl=55 time=32.171 ms
...

检查最终通过/失败的退出状态。

Answer 5

对于任何想要真正等待一段时间的人来说，考虑你的命令的时间可能很重要：

TIMEOUT_SEC=180
start_time="$(date -u +%s)"
while [ condition_or_just_true ]; do
  current_time="$(date -u +%s)"
  elapsed_seconds=$(($current_time-$start_time))
  if [ $elapsed_seconds -gt $TIMEOUT_SEC ]; then
    echo "timeout of $TIMEOUT_SEC sec"
    exit 1
  fi
  echo "another attempt (elapsed $elapsed_seconds sec)"
  some_command_and_maybe_sleep
done

Answer 6

我发现这可以满足我的需求：

function wait_for_success() {
    local timeout start_time end_time
    timeout=${TIMEOUT:-60}
    interval=${INTERVAL:-2}
    start_time=$(date +%s)
    end_time=$((start_time + timeout))
    while [ $(date +%s) -lt $end_time ]; do
        if $@; then
            return 0
        fi
        sleep $interval
    done
    >&2 echo "Timeout exceeded."
    return 1
}

Answer 7

我对 this 答案做了一些调整，让您可以打开是否达到超时，或者命令是否成功。另外，在此版本中每秒重试一次：

ELAPSED=0
started=$(mktemp)
echo "False" > $started
until the_command_here && echo "True" > $started || [ $ELAPSED -eq 30 ]
do
   sleep 1
   (( ELAPSED++ ))
done

if [[ $(cat $started) == "True" ]]                                                                                                                                                                                                                            
then                                                                                                                    
    echo "the command completed after $ELAPSED seconds"                                                                                              
else                                                                                                                    
    echo "timed out after $ELAPSED seconds"                                                                               
    exit 111                                                                                                            
fi