redirect all output in a bash script when using set -x

This is what I've just googled and I remember myself using this some time ago...

Use exec to redirect both standard output and standard error of all commands in a script:

#!/bin/bash
logfile=$$.log
exec > $logfile 2>&1

For more redirection magic check out Advanced Bash Scripting Guide - I/O Redirection.

If you also want to see the output and debug on the terminal in addition to in the log file, see redirect COPY of stdout to log file from within bash script itself.

If you want to handle the destination of the set -x trace output independently of normal STDOUT and STDERR, see bash storing the output of set -x to log file.

In my case, the script was being called multiple times from elsewhere, and I wasn't seeing everything, so I did an append instead, and it worked:

exec 1>>FILENAME 2>&1
set -x

To avoid confusion, be sure to delete FILENAME before each run.

the -x output goes to stderr, so to log it do:

set -x
exec 2>/tmp/mylog

To redirect stderr and stdout:

exec &>> $LOG_FILE_NAME

If you want to append to file. To overwrite file:

exec &> $LOG_FILE_NAME