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I am running a $command, in a instance of a screen, as a different user.
It's run by the equivalent of this command (more detailed at bottom):

su $USERNAME -c "screen -dmS $SCREENNAME $COMMAND"

and that works great. The problem is I want to redirect the output of $COMMAND to some logfile (e.g $LOGFILE).

Just adding > $LOGFILE to the end seems to read from screen instead of $COMMAND, so I am stumped as to what I should do. I've tried grouping it with parenthesis and braces, but that caused errors so I probably wasn't doing it correctly.

So how can I redirect the output of $COMMAND to $LOGFILE?


The code I am running is "equivalent" to this:

execute() {
  su $USERNAME -c "$*"
}
COMMAND="$SOMEDIR/$SOMEPROG $SOMEARGS"
execute screen -dmS $SCREENNAME $COMMAND

1 Answer 1

3

The problem is that not all shell parsing features get invoked if you pass the command directly to screen. So, the solution is to directly pass the command to a shell, which parses it as expected.

For example, assuming you use bash:
su $USERNAME -c "screen -dmS $SCREENNAME bash -c \"$COMMAND > $LOGFILE\""

(The escaped parentheses are so that the command is passed to bash as a whole, otherwise the problem with redirecting screen's output and not the $COMMAND's output would arise again)

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