将 stdout 捕获到一个变量，但仍然在控制台中显示它

我有一个 bash 脚本，它调用几个长时间运行的进程。出于处理原因，我想将这些调用的输出捕获到变量中。但是，因为这些是长时间运行的进程，所以我希望 rsync 调用的输出显示在 实时的的控制台中，而不是事后显示。

为此，我使用了 找到了的一种方法，但它依赖于将文本输出到/dev/stderr。我觉得输出到/dev/stderr 不是一种很好的做事方式。

VAR1=$(for i in {1..5}; do sleep 1; echo $i; done | tee /dev/stderr)


VAR2=$(rsync -r -t --out-format='%n%L' --delete -s /path/source1/ /path/target1 | tee /dev/stderr)


VAR3=$(rsync -r -t --out-format='%n%L' --delete -s /path/source2/ /path/target2 | tee /dev/stderr)

在上面的示例中，我调用了几次 rsync，希望在处理文件名时看到它们，但最终我还是希望在变量中输出，因为稍后我将解析它。

有没有一种“干净”的方法来实现这一点？

如果有区别的话，我使用的是 Ubuntu 12.04，bash 4.2.24。

44515 次浏览
小开

You can use more than three file descriptors. Try here:

http://tldp.org/LDP/abs/html/io-redirection.html

"Each open file gets assigned a file descriptor. [2] The file descriptors for stdin, stdout, and stderr are 0, 1, and 2, respectively. For opening additional files, there remain descriptors 3 to 9. It is sometimes useful to assign one of these additional file descriptors to stdin, stdout, or stderr as a temporary duplicate link."

The point is whether it's worth to make script more complicated just to achieve this result. Actually it's not really wrong, the way you do it.

小开
最佳答案

Duplicate &1 in your shell (in my example to 5) and use &5 in the subshell (so that you will write to stdout (&1) of the parent shell):

exec 5>&1
FF=$(echo aaa|tee >(cat - >&5))
echo $FF

This will print "aaa" two times, once because of the echo in the subshell, and the second time it prints the value of the variable.

In your code:

exec 5>&1
VAR1=$(for i in {1..5}; do sleep 1; echo $i; done | tee >(cat - >&5))
# use the value of VAR1
小开

Op De Cirkel's answer has the right idea. It can be simplified even more (avoiding use of cat):

exec 5>&1
FF=$(echo aaa|tee /dev/fd/5)
echo $FF
小开

Here's an example capturing both stderr and the command's exit code. This is building on the answer by Russell Davis.

exec 5>&1
FF=$(ls /taco/ 2>&1 |tee /dev/fd/5; exit ${PIPESTATUS[0]})
exit_code=$?
echo "$FF"
echo "Exit Code: $exit_code"

If the folder /taco/ exists, this will capture its contents. If the folder doesn't exist, it will capture an error message and the exit code will be 2.

If you omit 2>&1then only stdout will be captured.

小开

If by "the console" you mean your current TTY, try

variable=$(command with options | tee /dev/tty)

This is slightly dubious practice because people who try to use this sometimes are surprised when the output lands somewhere unexpected when they don't have a TTY (cron jobs etc).


提交答案