如何在 bash 中撤销 exec > /dev/null？
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How to undo exec > /dev/null in bash?
提问by user2267134
I used
我用了
exec > /dev/null
to suppress output.
来抑制输出。
Is there a command to undo this? (Without restarting the script.)
是否有命令可以撤消此操作？（无需重新启动脚本。）
回答by Charles Duffy
To do it right, you need to copy the original FD 1 somewhere else before repointing it to /dev/null. In this case, I store a backup on FD 5:
要做到这一点，您需要先将原始 FD 1 复制到其他地方，然后再将其重新指向 /dev/null。在这种情况下，我将备份存储在 FD 5 上：
exec 5>&1 >/dev/null
...
exec 1>&5
Another option is to redirect stdout within a block rather than using exec:
另一种选择是在块内重定向标准输出而不是使用exec：
{
...
} >/dev/null
回答by Vaughn Cato
If you just want to get output again at the command prompt, you can do this:
如果您只想在命令提示符下再次获得输出，您可以这样做：
exec >/dev/tty
If you are creating a script, and you want to have the output of a certain group of commands redirected, put those commands in braces:
如果您正在创建脚本，并且希望重定向某组命令的输出，请将这些命令放在大括号中：
{
command
command
} >/dev/null
回答by Berkant
Save the original output targets beforehand.
预先保存原始输出目标。
# $$ = the PID of the running script instance
STDOUT=`readlink -f /proc/$$/fd/1`
STDERR=`readlink -f /proc/$$/fd/2`
And restore them again using exec.
并使用exec.
exec 1>$STDOUT 2>$STDERR
If you use /dev/ttyfor restoration as in the answers above, contrary to this, you won't be able to do redirections in call-level, e.g. bash script.sh &>/dev/nullwon't work.
如果您/dev/tty像上面的答案一样用于恢复，与此相反，您将无法在呼叫级别进行重定向，例如bash script.sh &>/dev/null不起作用。
回答by Роман Горбач
To restore stdout I use
要恢复我使用的标准输出
unset &1
回答by chepner
Not really, as that would require changing the state of a running process. Even assuming you could, whatever you wrote before resetting standard output is truly, completely gone, as it was sent to the bit bucket.
不是真的，因为这需要更改正在运行的进程的状态。即使假设你可以，在重置标准输出之前你写的任何东西都真的，完全消失了，因为它被发送到位桶。
