How to redirect standard (stderr) error in bash

You can redirect standard error (stderr) in bash to a file, or to another standard stream, such as standard output (stdout), using the following syntax:

command 2> file.txt

This will redirect the standard error stream from the "command" to the file "file.txt".

To redirect standard error to standard output, which can then be redirected to a file, you can use the following syntax:

command 2>&1 | tee file.txt

This will pipe both standard error and standard output from the "command" to the "tee" utility, which writes the data to both the screen and the file "file.txt".