What does 2>/dev/null mean?

The > operator redirects the output usually to a file but it can be to a device. You can also use >> to append.

If you don't specify a number then the standard output stream is assumed, but you can also redirect errors:

> file redirects stdout to file
1> file redirects stdout to file

2> file redirects stderr to file

&> file redirects stdout and stderr to file
> file 2>&1 redirects stdout and stderr to file

/dev/null is the null device it takes any input you want and throws it away. It can be used to suppress any output.

Note that > file 2>&1 is an older syntax which still works, &> file is neater, but would not have worked on older systems.

In short, it redirects stderr (fd 2) to the black hole (discards the output of the command).

Some commonly used pattern for redirection:

command > /dev/null 2>&1 &

Run command in the background, discard stdout and stderr

command >> /path/to/log 2>&1 &

Run command, append stdout and stderr to a log file.

In Bash 4+, a shorter (but less readable) form is functional

command &>> /path/to/log

/dev/null is treated as black hole in Linux/Unix, so you can put anything into this but you will not be able to get it back from /dev/null.

Further, 2> means that you are redirecting (i.e. >) the stderr (i.e. 2) into the black hole (i.e. /dev/null)

Your command is:

grep -i 'abc' content 2>/dev/null 

Don't try to end with another forward slash like this - 2>/dev/null/ (it's not a directory).