linux - 使用命令行在启动后重定向进程的 STDERR/STDOUT？

Question

在shell中你可以做重定向，> <等等，但是在程序启动之后呢？

这就是我问这个问题的方式，在我的终端后台运行的程序不断输出烦人的文本。这是一个重要的过程，所以我必须打开另一个 shell 以避免文本。我希望能够 >/dev/null或其他一些重定向，以便我可以继续在同一个 shell 中工作。

Answer 1

关闭并重新打开您的 tty(即注销并重新打开，这也可能会终止您在进程中的一些后台进程)您只有一个选择:

• 使用 gdb 附加到有问题的进程，然后运行:
  • p dup2(open("/dev/null", 0), 1)
  • p dup2(open("/dev/null", 0), 2)
  • 分离
  • 退出

例如:

$ tail -f /var/log/lastlog &
[1] 5636

$ ls -l /proc/5636/fd
total 0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 0 -> /dev/pts/0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 1 -> /dev/pts/0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 2 -> /dev/pts/0
lr-x------ 1 myuser myuser 64 Feb 27 07:36 3 -> /var/log/lastlog

$ gdb -p 5636
GNU gdb 6.8-debian
Copyright (C) 2008 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Attaching to process 5636
Reading symbols from /usr/bin/tail...(no debugging symbols found)...done.
Reading symbols from /lib/librt.so.1...(no debugging symbols found)...done.
Loaded symbols for /lib/librt.so.1
Reading symbols from /lib/libc.so.6...(no debugging symbols found)...done.
Loaded symbols for /lib/libc.so.6
Reading symbols from /lib/libpthread.so.0...(no debugging symbols found)...done.
[Thread debugging using libthread_db enabled]
[New Thread 0x7f3c8f5a66e0 (LWP 5636)]
Loaded symbols for /lib/libpthread.so.0
Reading symbols from /lib/ld-linux-x86-64.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib64/ld-linux-x86-64.so.2

(no debugging symbols found)
0x00007f3c8eec7b50 in nanosleep () from /lib/libc.so.6

(gdb) p dup2(open("/dev/null",0),1)
[Switching to Thread 0x7f3c8f5a66e0 (LWP 5636)]
$1 = 1

(gdb) p dup2(open("/dev/null",0),2)
$2 = 2

(gdb) detach
Detaching from program: /usr/bin/tail, process 5636

(gdb) quit

$ ls -l /proc/5636/fd
total 0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 0 -> /dev/pts/0
lrwx------ 1 myuser myuser 64 Feb 27 07:36 1 -> /dev/null
lrwx------ 1 myuser myuser 64 Feb 27 07:36 2 -> /dev/null
lr-x------ 1 myuser myuser 64 Feb 27 07:36 3 -> /var/log/lastlog
lr-x------ 1 myuser myuser 64 Feb 27 07:36 4 -> /dev/null
lr-x------ 1 myuser myuser 64 Feb 27 07:36 5 -> /dev/null

您也可以考虑:

• 使用屏幕； screen 提供了几个虚拟 TTY，您可以在无需打开新的 SSH/telnet/etc session 之间切换
• 使用 nohup;这使您可以关闭并重新打开 session ，而不会丢失...进程中的任何后台进程。