Using exec and tee to redirect logs to stdout and a log file in the same time [duplicate]

Question

In a bash script, how can I redirect all standard outputs to a log file and tee the output on the screen using exec ?

log_file="$HOME/logs/install.txt-`date +'%Y-%m-%d_%H-%M-%S'`"
[ -f "$log_file" ] || touch "$log_file"
exec 1>> $log_file 2>&1

This code redirect all the log to the log file but not to the screen .

Answer 1

Use process substitution with & redirection and exec:

exec &> >(tee -a "$log_file")
echo "This will be logged to the file and to the screen"

$log_file will contain the output of the script and any subprocesses, and the output will also be printed to the screen.

• >(...) starts the process ... and returns a file representing its standard input.

• exec &> ... redirects both standard output and standard error into ... for the remainder of the script (use just exec > ... for stdout only).

• tee -a appends its standard input to the file, and also prints it to the screen.

Answer 2

exec >> $log_file 2>&1 && tail $log_file