macos 如何从已经运行的进程中捕获标准输出
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How can I capture the stdout from a process that is ALREADY running
提问by theraccoonbear
I have a running cron job that will be going for a while and I'd like to view its stdout. I don't know how important the fact that the process was started by cron is, but I figure I'd mention it. This is on OSX so, I don't have access to things like... /proc/[pid]/..., or truss, or strace. Suggestions of executing with IO redirection (e.g. script > output & tail -f output) are NOT acceptable, because this process is 1) already running, and 2) can't be stopped/restarted with redirection. If there are general solutions that will work across various Unices, that'd be ideal, but specifically I'm trying to accomplish this on a Mac right now.
我有一个正在运行的 cron 作业，它将持续一段时间，我想查看它的标准输出。我不知道这个过程是由 cron 启动的这一事实有多重要，但我想我会提到它。这是在 OSX 上，所以我无法访问诸如... /proc/[pid]/...、truss 或 strace 之类的东西。使用 IO 重定向（例如script > output & tail -f output）执行的建议是不可接受的，因为此进程 1) 已经在运行，并且 2) 无法通过重定向停止/重新启动。如果有适用于各种 Unices 的通用解决方案，那将是理想的，但具体而言，我现在正试图在 Mac 上完成此任务。
回答by mpyw
True solution for OSX
OSX 的真正解决方案
Write the following function to your ~/.bashrcor ~/.zshrc.
将以下函数写入您的~/.bashrc或~/.zshrc.
capture() {
sudo dtrace -p "" -qn '
syscall::write*:entry
/pid == $target && arg0 == 1/ {
printf("%s", copyinstr(arg1, arg2));
}
'
}
Usage:
用法：
example@localhost:~$ perl -e 'STDOUT->autoflush; while (1) { print "Hello\n"; sleep 1; }' >/dev/null &
[1] 97755
example@localhost:~$ capture 97755
Hello
Hello
Hello
Hello
...
https://github.com/mivok/squirrelpouch/wiki/dtrace
https://github.com/mivok/squirrelpouch/wiki/dtrace
NOTE:
笔记：
You must disable dtracerestriction on El Capitan or later.
您必须禁用dtrace对 El Capitan 或更高版本的限制。
csrutil enable --without dtrace
回答by Mark Renouf
DISCLAIMER: No clue if Mac has this. This technique exists on Linux. YMMV.
免责声明：不知道 Mac 是否有这个。这种技术存在于 Linux 上。天啊。
You can grab stdout/err from /proc (assuming proper privileges):
您可以从 /proc 获取 stdout/err（假设有适当的权限）：
PID=$(pidof my_process)
tail -f /proc/$PID/fd/1
Or grab everything remaining in the buffer to a file:
或者将缓冲区中剩余的所有内容抓取到一个文件中：
cat /proc/$PID/fd/1
PS: fd/1 is stdout, fd/2 is stderr.
PS：fd/1 是标准输出，fd/2 是标准错误。
EDIT: Alex brown> Mac does not have this, but it's a useful tip for Linux.
编辑：Alex brown> Mac 没有这个，但它对 Linux 来说是一个有用的提示。
回答by Alex Brown
use dtruss -p <PID>, or even rwsnoop -p <PID>.
使用dtruss -p <PID>, 甚至rwsnoop -p <PID>.
回答by LaC
回答by Sodved
I think the fact you started with cron could save you. Under linux any standard output of a cron job is mailed to the unix mail account of the user who owns the job. Not sure about OSX though. Unfortunately you will have to wait for the the job to finish before the mail is sent and you can view the output.
我认为你从 cron 开始的事实可以拯救你。在 linux 下，cron 作业的任何标准输出都会邮寄到拥有该作业的用户的 unix 邮件帐户。虽然不确定 OSX。不幸的是，您必须等待作业完成才能发送邮件，然后才能查看输出。
