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This post answers the question, "How can I log all commands and their outputs, including errors, to a file?"
Log all Commands and their Outputs, Including Errors, to a File
exec > >(tee -i output.log) 2>&1Description
Process Substitution Setup:
The shell identifies the process substitution part >(tee -i output.log).
A subshell is created to execute tee -i output.log.
The subshell running tee provides a file descriptor (let's call it FD1) that acts like a temporary file.
Exec Command with Stdout Redirection:
exec > FD1: The exec command changes the file descriptor for the current shell.
The standard output (stdout, file descriptor 1) of the current shell is redirected to FD1 (the file descriptor provided by the tee subshell).
Stderr Redirection to Stdout:
2>&1: The standard error (stderr, file descriptor 2) is redirected to the current destination of stdout (file descriptor 1).
Since stdout has already been redirected to FD1 (the tee subshell), stderr will also be redirected to FD1.
Execution of tee Command:
The tee command reads from FD1 (which now receives both stdout and stderr from the shell).
tee writes the received output to both output.log and the console (stdout of the tee subshell).
Example Application
Trace and capture bash script execution.
set -x
exec > >(tee -i output.log) 2>&1
bash scriptAdditional Information
See:
