在失败的管道杀下一个命令（击） [英] Kill next command in pipeline on failure (Bash)

问题描述

我有我运行一个流式备份脚本如下：

I have a streaming backup script which I'm running as follows:

./backup_script.sh | aws s3 cp - s3://bucket/path/to/backup

的 AWS 命令流标准输入到云存储在原子的方式。如果过程没有EOF中断，上传被中止。

The aws command streams stdin to cloud storage in an atomic way. If the process is interrupted without an EOF, the upload is aborted.

我要的 AWS 过程中被杀死，如果 ./ backup_script.sh 退出以非零退出code。

I want the aws process to be killed if ./backup_script.sh exits with a non-zero exit code.

任何bash的把戏这样做？

Any bash trick for doing this?

编辑：
你可以用这个脚本测试您的解决方案：

You can test your solution with this script:

#!/usr/bin/env python
import signal
import sys
import functools

def signal_handler(signame, signum, frame):
    print "Got {}".format(signame)
    sys.exit(0)

signal.signal(signal.SIGTERM, functools.partial(signal_handler, 'TERM'))
signal.signal(signal.SIGINT, functools.partial(signal_handler, 'INT'))

for i in sys.stdin:
    pass

print "Got EOF"

例如：

$ grep --bla | ./sigoreof.py
grep: unrecognized option `--bla'
usage: grep [-abcDEFGHhIiJLlmnOoqRSsUVvwxZ] [-A num] [-B num] [-C[num]]
    [-e pattern] [-f file] [--binary-files=value] [--color=when]
    [--context[=num]] [--directories=action] [--label] [--line-buffered]
    [--null] [pattern] [file ...]
Got EOF

我想 ./ sigoreof.py 与信号终止。

推荐答案

它使用进程替换，而不是命名管道的一个简短的脚本是：

A short script which uses process substitution instead of named pipes would be:

#!/bin/bash

exec 4> >( ./second-process.sh )
./first-process.sh >&4  &
if ! wait $! ; then echo "error in first process" >&2; kill 0; wait; fi

它与一个FIFO很像，基本上都采用的FD作为IPC而不是文件名的信息载体。

It works much like with a fifo, basically using the fd as the information carrier for the IPC instead of a file name.

二话：我不知道是否有必要关闭FD 4;我会假设，在脚本退出外壳关闭所有打开的文件。

Two remarks: I wasn't sure whether it's necessary to close fd 4 ; I would assume that upon script exit the shell closes all open files.

和我无法弄清楚如何获得进程的PID的过程中替换（别人吗？至少在我的cygwin通常的 $！没的工作。）因此，我使出了组，这可能不是理想地杀死所有进程（但我不能完全肯定的语义）。

And I couldn't figure out how to obtain the PID of the process in the process substitution (anybody? at least on my cygwin the usual $! didn't work.) Therefore I resorted to killing all processes in the group, which may not be desirable (but I'm not entirely sure about the semantics).

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