BASH Shell: How To Redirect stderr To stdout ( redirect stderr to a File )

Q. How do I redirect stderr to stdout? How do I redirect stderr to a file?

A. Bash and other modern shell provides I/O redirection facility. There are 3 default standard files (standard streams) open:
[a] stdin - Use to get input (keyboard) i.e. data going into a program.

[b] stdout - Use to write information (screen)

[c] stderr - Use to write error message (screen)

Understanding I/O streams numbers

The Unix / Linux standard I/O streams with numbers:

Handle	Name	Description
0	stdin	Standard input
1	stdout	Standard output
2	stderr	Standard error

Redirecting the standard error stream to a file

The following will redirect program error message to a file called error.log:
$ program-name 2> error.log
$ command1 2> error.log

Redirecting the standard error (stderr) and stdout to file

Use the following syntax:
$ command-name &>file
OR
$ command > file-name 2>&1
Another useful example:
# find /usr/home -name .profile 2>&1 | more

Redirect stderr to stdout

Use the command as follows:
$ command-name 2>&1