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# 1  
Old 09-10-2001
Question shell problem

[ "$DEBUG" = Y ] && set -x && echo "enter tablespace_end_backup" >&2

Can you tell me what's mean above?

thanx
# 2  
Old 09-10-2001
Well when two commands are linked together by && the second one is executed only if the first succeeds. So something like:

[ $DEBUG = y ] && echo DEBUG is set >&2

will echo "DEBUG is set" if and only if $DEBUG is equal to y. It's a one line "if" statement. The >&2 sends the output of the echo to stderr rather than stdout.

"set -x" will always succeed. So the second && is a way to do two statements based on the results of the first test. I think it's poor syntax and I would use:

[ "$DEBUG" = Y ] && { set -x ; echo "enter tablespace_end_backup" >&2 ; }

Of course, you can strongly argue for a full "if" statement in this case, but many programmers (including me) try to keep debug statements to one like so they can easily be commented out to improve performance.
 

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