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1.) stdout to a file

The output of a command will redirect to another file.

Eg:          ls -l > list.txt

2.) stderr to a  file

The following command will redirect the  stderr ouput of a program to a new file.

Eg:       grep sibu * 2> grep-errors.txt

Here, a file called ‘grep-errors.txt’ will be created and it will contain what you would see the stderr portion of the output of the ‘grep sibu *’ command.

3.) Stdout to Stderr

This will cause the stderr ouput of a program to be written to the same filedescriptor than stdout.

Eg:          grep sibu * 1>&2

Here, the stdout portion of the command is sent to stderr..

4.): stderr to stdout

This will cause the stderr ouput of a program to be written to the same filedescriptor than stdout.

Eg:       grep * 2>&1

Here, the stderr portion of the command is sent to stdout.

5.) stderr and stdout 2 file

This will place every output of a program to a file. This is suitable sometimes for cron entries, if you want a command to pass in absolute silence.

Eg:       rm -f $(find / -name core) &> /dev/null