bash 通过管道从子shell获取退出代码
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Get exit code from subshell through the pipes
提问by ДМИТРИЙ МАЛИКОВ
How can I get exit code of wgetfrom the subshell process?
如何wget从子shell进程中获取退出代码？
So, main problem is that $?is equal 0. Where can $?=8be founded?
所以，主要问题是$?等于0。在哪里可以$?=8成立？
$> OUT=$( wget -q "http://budueba.com/net" | tee -a "file.txt" ); echo "$?"
0
It works without tee, actually.
tee实际上，它没有.
$> OUT=$( wget -q "http://budueba.com/net" ); echo "$?"
8
But ${PIPESTATUS}array (I'm not sure it's related to that case) also does not contain that value.
但是${PIPESTATUS}数组（我不确定它与那种情况有关）也不包含该值。
$> OUT=$( wget -q "http://budueba.com/net" | tee -a "file.txt" ); echo "${PIPESTATUS[1]}"
$> OUT=$( wget -q "http://budueba.com/net" | tee -a "file.txt" ); echo "${PIPESTATUS[0]}"
0
$> OUT=$( wget -q "http://budueba.com/net" | tee -a "file.txt" ); echo "${PIPESTATUS[-1]}"
0
So, my question is - how can I get wget's exit code through teeand subshell?
所以，我的问题是 - 我怎样才能wget通过teesubshell获取退出代码？
If it could be helpful, my bash version is 4.2.20.
如果有帮助，我的 bash 版本是4.2.20.
回答by Christian.K
By using $()you are (effectively) creating a subshell. Thus the PIPESTATUSinstance you need to look at is only available inside your subshell (i.e. inside the $()), since environment variables do not propagate from child to parent processes.
通过使用$()您（有效地）创建了一个子shell。因此，PIPESTATUS您需要查看的实例仅在您的子外壳内（即在 内$()）可用，因为环境变量不会从子进程传播到父进程。
You could do something like this:
你可以这样做：
OUT=$( wget -q "http://budueba.com/net" | tee -a "file.txt"; exit ${PIPESTATUS[0]} );
echo $? # prints exit code of wget.
You can achieve a similar behavior by using the following:
您可以使用以下方法实现类似的行为：
OUT=$(wget -q "http://budueba.com/net")
rc=$? # safe exit code for later
echo "$OUT" | tee -a "file.txt"
回答by Mrskman
Beware of this when using localvariables:
使用local变量时要注意这一点：
local OUT=$(command; exit 1)
echo $? # 0
OUT=$(command; exit 1)
echo $? # 1
回答by maxdev137
Copy the PIPESTATUS array first. Any reads destroy the current state.
首先复制 PIPESTATUS 数组。任何读取都会破坏当前状态。
declare -a PSA
cmd1 | cmd2 | cmd3
PSA=( "${PIPESTATUS[@]}" )
I used fifos to solve the sub-shell/PIPESTATUS problem. See
bash pipestatus in backticked command?
I also found these useful:
bash script: how to save return value of first command in a pipeline?
and https://unix.stackexchange.com/questions/14270/get-exit-status-of-process-thats-piped-to-another/70675#70675
我使用fifos来解决子shell/PIPESTATUS问题。在反引号命令中看到
bash pipestatus 吗？
我还发现这些很有用：
bash 脚本：如何在管道中保存第一个命令的返回值？
和https://unix.stackexchange.com/questions/14270/get-exit-status-of-process-thats-piped-to-another/70675#70675
