使用exec和写入屏幕的Bash脚本全局重定向

Question

我有一个大的bash脚本,我想全局将所有stdout/stderr重定向到一个文件,除了一些进度指示器,如特定的回显消息.例如,请考虑以下脚本

#!/bin/bash

# all stdout and stderr go to out.log
exec &> out.log

special_echo "starting"

# many other commands go here
# which output both the stdout and stderr
# also some special_echo commands in here,
# for example
echo "msg1"
special_echo "middle"
echo "msg2" >&2

special_echo "finished"

当它运行时,输出应该是

$ ./script
starting
middle
finished
$

但是,out.log应该包含

msg1
msg2

如何实现special_echo功能？我已经尝试使用文件描述符并回显,但无法让它显示在屏幕上.

有没有办法实现这一点,而无需将重定向添加到每一行或做这样的答案？

Answer 1

是的,使用另一个文件描述符是要走的路:

#!/bin/bash

exec 3>&1
special_echo () {
    echo "$@" >&3
}

exec &> out.log

special_echo "starting"
echo "msg1"
special_echo "middle"
echo "msg2" >&2
special_echo "finished"