Could someone explain this try/catch alternative in bash?

问题

So I found out that bash does not handle exceptions (there is no try/catch). For my script, I would like to know if a command was successful or not.

This is the part of my code right now:

command = "scp -p$port $user:$password@$host:$from $to"
$command 2>/dev/null

if (( $? == 0 )); then
    echo 'command was successful'
else
    echo 'damn, there was an error'
fi

The things I don't understand are:

• line 3, why do I have to put the 2 behind the $command?
• line 5, what exactly is it with this $?

回答1:

$? means the return code of the last executed command.

2> means redirecting the stderr (standard error stream) output to /dev/null.

回答2:

Just FYI, this will also work:

if some_command 2>/dev/null ; then
    echo 'command was successful'
else
    echo 'damn, there was an error'
fi

来源：https://stackoverflow.com/questions/14964529/could-someone-explain-this-try-catch-alternative-in-bash