bash 如何将所有输出重定向到 /dev/null？
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How can I redirect all output to /dev/null?
提问by Benubird
I want to run a program (google-chrome) in the background, but prevent it from outputting any messages to the terminal.
我想google-chrome在后台运行一个程序 ( )，但阻止它向终端输出任何消息。
I tried doing this:
我尝试这样做：
google-chrome 2>&1 1>/dev/null &
However, the terminal still fills up without messages like:
但是，终端仍然填满而没有如下消息：
[5746:5746:0802/100534:ERROR:object_proxy.cc(532)] Failed to call method: org.chromium.Mtpd.EnumerateStorag...
[5746:5746:0802/100534:ERROR:object_proxy.cc(532)] 调用方法失败：org.chromium.Mtpd.EnumerateStorag...
What am I doing wrong? How do I redirect allthe output to /dev/null?
我究竟做错了什么？如何将所有输出重定向到/dev/null？
回答by Michael Martinez
Redirection operators are evaluated left-to-right. You wrongly put 2>&1first, which points 2to the same place, as 1currently is pointed to which is the local terminal screen, because you have not redirected 1yet. You need to do either of the following:
重定向运算符从左到右计算。你错误地把2>&1指向2同一个地方的第一个指向了1当前指向的本地终端屏幕，因为你还没有重定向1。您需要执行以下任一操作：
2>/dev/null 1>/dev/null google-chrome &
Or
或者
2>/dev/null 1>&2 google-chrome &
The placement of the redirect operators in relation to the command does not matter. You can put them before or after the command.
与命令相关的重定向运算符的位置无关紧要。您可以将它们放在命令之前或之后。
回答by user1146332
In the section Redirection, Bash's reference manual says:
在Redirection部分，Bash 的参考手册说：
The operator
[n]>&wordis used [...] to duplicate output file descriptors
该运算符
[n]>&word用于 [...] 复制输出文件描述符
To redirect both standard error and standard output to fileyou should use the form
要将标准错误和标准输出重定向到file您应该使用表单
&>file
With regard to your case, that means substitute
关于你的情况，这意味着替代
2>&1 1>/dev/null
with
和
&>/dev/null
回答by user1146332
It seems that syntax is different:
似乎语法不同：
./a.out 1>/dev/null 2>&1 &
See the devices for FD = 2 are different when ./a.out 1>/dev/null 2>&1and ./a.out 2>&1 1>/dev/null &
看到 FD = 2 的设备在./a.out 1>/dev/null 2>&1和./a.out 2>&1 1>/dev/null &
1) FD=2 points to /dev/null
1) FD=2 指向 /dev/null
>./a.out 1>/dev/null 2>&1 &
[1] 21181
>lsof -p `pidof a.out`
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
a.out 21181 xxxxxxxxxxxxxxx 0u CHR 136,43 0t0 46 /dev/pts/43
a.out 21181 xxxxxxxxxxxxxxx 1w CHR 1,3 0t0 3685 /dev/null
a.out 21181 xxxxxxxxxxxxxxx 2w CHR 1,3 0t0 3685 /dev/null
2) FD=2 points to /dev/pts/43
2) FD=2 指向 /dev/pts/43
>./a.out 2>&1 1>/dev/null &
[1] 25955
>lsof -p `pidof a.out`
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
a.out 25955 xxxxxxxxxxxxxxx 0u CHR 136,43 0t0 46 /dev/pts/43
a.out 25955 xxxxxxxxxxxxxxx 1w CHR 1,3 0t0 3685 /dev/null
a.out 25955 xxxxxxxxxxxxxxx 2u CHR 136,43 0t0 46 /dev/pts/43
