🎯Redirect standard input/output/error for shell commands.

redirection_commands_Shell.md

There are three I/O devices available on the command line:

1.standard input - 0

2.standard output - 1

3.standard error - 2

To redirect standard output (the default output) to a file (and overwrite the file), use:

command > file.log

To append to file.log, use two >

command >> file.log

To redirect standard error to the file.log, use

command 2> file.log

And to append

command 2>> file.log

To combine the outputs into one stream and send them all to one place

command > file.log 2>&1

This sends 2 (standard error) into 1 (standard output), and sends standard output to file.log

Notice that it's also possible to redirect standard input into a command that expects standard input

command << file.txt

---

Hide standard output:

./command >/dev/null

Hide standard output and standard error:

./command >/dev/null 2>&1

Hide standard output and standard error and release terminal (run the command in the background):

./command >/dev/null 2>&1 &

For more details, check out the Advanced Bash Scripting Guide.

note: this is collected from answer given here.