2>&1 in command means??

References..

0 = standard input (stdin)

1 = standard output (stdout) 

2 = standard error (stderr)

Hence, we can use command > output.log to print the std output stream, which is an implicit meaning of command 1>output.log

Thus, the annex 2>&1 means print the std error to the same place as the std output. 

Moreover, the we can hide the std output from printing out by using 2>/dev/null.

Thanks to: https://linuxize.com/post/bash-redirect-stderr-stdout/

Learning bash: https://iridakos.com/programming/2018/03/01/bash-programmable-completion-tutorial