How do I let my script not only output to screen but also record its output to a file? I want this to be done automatically within the script, rather than requiring the user to pipe the output through
tee or some other solution.
script.sh < inputfile | tee logfile
You didn't specify, so I'm assuming this is a bash script. According to
man bash (emphasis mine):
exec [-cl] [-a name] [command [arguments]]
If command is specified, it replaces the shell. No new process is created. The arguments become the arguments to command. If the -l option is supplied, the shell places a dash at the beginning of the zeroth argument passed to command. This is what login(1) does. The -c option causes command to be executed with an empty environment. If a is supplied, the shell passes name as the zeroth argument to the executed command. If command cannot be executed for some reason, a non-interactive shell exits, unless the execfail shell option is enabled. In that case, it returns failure. An interactive shell returns failure if the file cannot be executed. If command is not specified, any redirections take effect in the current shell, and the return status is 0. If there is a redirection error, the return status is 1.
So you can use process substitution to run a copy of
tee that's logging to a file, and redirect your stdout to that
tee so that it prints and logs at once:
exec > >(tee /path/to/log-file)
If you also want to capture stderr, you need to merge it with stdout:
Or just capture both at once with:
exec &> >(tee /path/to/log-file)