Am Montag, 4. September 2006 06:56 schrieb Bruce Dubbs: > Mag. Leonhard Landrock wrote: > > Hi! > > > > When is the following expression true? > > > > if [ -z "$INPUTRC" -a ! -f "$HOME/.inputrc" ] ; then > > INPUTRC=/etc/inputrc > > fi > > I think you are getting confused by the -a here.
Exactly that was the point where I missed the right way. > It *is* a bit ambiguous. > The [ expr ] construct is a synonym for 'test'. I know that, thanks. :-) > Look at the > 'test' builtin in the bash man page (quite a way down): > > expr1 -a expr2 > True if both expr1 and expr2 are true. Yes!!! That's the point. :-) Funny that I missed it. > The -a here is an expression operator between two operands, not a > literal conditional expression like -z or ! -f in this example. > > Note: We could have made it really confusing by the valid statement: > > if [ -z "$INPUTRC" -a ! -a "$HOME/.inputrc" ] ; then > ... OK. Let's see wether I can decrypt that. ;-) If 1.) <-z "$INPUTRC"> says: length of string "$INPUTRC" is zero 2.) <-a> says: True if both "expr1" and "expr2" are true. "expr1" beeing <-z "$INPUTRC"> and "expr2" beeing <! "expr3"> 3.) <! "expr3"> says: Not "expr3" with <-a "$HOME/.inputrc"> beeing "expr3". 4.) <-a "$HOME/.inputrc"> says: True if file "$HOME/.inputrc" exists. then do ... > :) > > -- Bruce Leonhard. -- http://linuxfromscratch.org/mailman/listinfo/blfs-support FAQ: http://www.linuxfromscratch.org/blfs/faq.html Unsubscribe: See the above information page
