How to redirect output of an entire ZSH shell script from within script itself?-CodePudding

So I want to log the output (stdout & stderr) of my non-interactive zsh shell scripts to both stdout and a log file, and to configure that capability from within the script itself.

With bash scripts, I've used the following and it works perfectly:

#!/bin/bash
exec &> >(tee -a /path/to/logfile)

Everything that follows prints both to stdout and to a log file.

But when I change the script to run with #!/bin/zsh, the script will hang when it gets to the exec line.

For example, if the script were this:

#!/bin/zsh
echo 'test'
exec &> >(tee -a /path/to/logfile)

Then when running it, stdout will hang showing this:

 test_script.sh:2> echo test

Annoyingly, in the hanged state, Ctrl-C won't kill the process. Only way I know to get control of my terminal back is to background the process with Ctrl-Z and then kill the pid. (Took me a while to figure that out.)

Anyway, I'd like to know how I can achieve the same result in zsh. Ideally I'd also really like to understand why zsh is behaving differently from bash.

Thank you!

CodePudding user response：

You can't do it that way in zsh, as after exec >(cmd), zsh will be wanting to wait for the process substitution to finish before carrying on.

You could however do:

#! /bin/zsh -
{
  # the whole script goes here
} >&1 >> file.log 2>&1

(no need for tee, as zsh can redirect to multiple files using its all internal teeing when you redirect some fd several times).

CodePudding user response：

I (finally) discovered a way to do this in a way compatible with both bash and zsh:

#!/bin/bash or #!/bin/zsh

exec > >(tee -a path/to/logfile) 2>&1

As a bonus, I also discovered how to change redirection of logging to different files within the same script.

#!/bin/bash or #!/bin/zsh

exec 3>&1
exec > >(tee -a path/to/logfile-1) 2>&1

echo "Copies stdout and stderr to first logfile"

exec >&3
exec > >(tee -a path/to/logfile-2) 2>&1

echo "Copies stdout and stderr to second logfile (and not the first)"

I admit I don't fully understand why this works, and why exec behaves differently with what I tried before, but I'm using this method now with no issues.

Thank you to all who've responded!