bash 在不使用 stderr 的情况下将 stdout 重定向到文件后写入终端？
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Write to terminal after redirecting stdout to a file without using stderr?
提问by Dagg Nabbit
I have two shell scripts, one that serves as the main "program" and another that serves as a "library."
我有两个 shell 脚本，一个用作主“程序”，另一个用作“库”。
In several places in the "program," I'll do something like: log "$thing" >> "$logfile", where logis a function defined in the "library."
在“程序”的几个地方，我会做这样的事情：log "$thing" >> "$logfile"，log“库”中定义的函数在哪里。
# program.sh
logfile="log.txt"
stuff="hahah heheh hoho"
. library.sh
for thing in $stuff; do
log "$thing" >> "$logfile"
done
My question: Is there a way to redirect someof the output from the function back to the terminal withoutusing stderr?
我的问题：有没有办法在不使用的情况下将函数的某些输出重定向回终端？stderr
# library.sh
log () {
# This gets written to the log
echo "`date --rfc-3339=seconds`: "
# How to write this to the terminal *without* using stderr?
echo "Info: Message written to log." >&2
}
I want to avoid the use of stderrbecause in my actual program, there's an option to redirect errors to a file, but the messages I want to send to the terminal are informational, not errors, and should always show up on the terminal.
我想避免使用，stderr因为在我的实际程序中，有一个选项可以将错误重定向到文件，但我想发送到终端的消息是信息性的，而不是错误，并且应该始终显示在终端上。
回答by Ignacio Vazquez-Abrams
Open /dev/ttyon another FD.
/dev/tty在另一个 FD 上打开。
exec 0< /dev/null
exec 1> /dev/null
exec 2> /dev/null
exec 3> /dev/tty
echo 'Hello, World!' >&3
回答by sarnold
You can write directly to /dev/ttyeach time you want to write to the terminal:
/dev/tty每次要写入终端时都可以直接写入：
echo "hello world" > /dev/tty
For a small example:
举个小例子：
$ cat writer.sh
#!/bin/sh
echo "standard output"
echo "standard error" >&2
echo "direct to terminal" > /dev/tty
$ ./writer.sh > /tmp/out 2> /tmp/err
direct to terminal
$ cat /tmp/out
standard output
$ cat /tmp/err
standard error
$
