Jason Stelzer on 17 Sep 2009 07:33:07 0700 
Thanks, again, that's why I asked. There's no real user input involved, just properties files that are created and reviewed before they're executed. The use of bc is something I really should have thought of myself. Thanks for pointing me in a much more technically correct direction. On Thu, Sep 17, 2009 at 1:47 AM, Paul L. Snyder <plsnyder@drexel.edu> wrote: > On September 16, 2009, "Jason Stelzer" <jason.stelzer@gmail.com> wrote: > >> Well, to be fair.... >> >> First, thanks, that's a good idea. I'll just do that. >> >> Second, I really just need to always round up the the nearest whole number. > > Just? > > I took another look at your code snippet. It will indeed give you the > ceiling of "something", as long as that something is the result of > dividing two positive (or two negative) integer numbers. This may be > sufficient for your purposes. You could avoid using the _MY_CEIL > construct you dislike by employing command substitution as used in my > previous suggestion, at the price of spawning a subshell. > > It's worth noting that bash is not giving you the floor as the result of > arithmetic operations, it is giving you the result of integer division. > This is the same as the floor only if both numbers are either positive > or negative. If one of the numbers is negative, the result of > $(( 5 / 3 )) will be 1, not 2. > > If you want to do some math in bc rather than (as I originally > assumed) just give it a floatingpoint number, you can make it > safe for division with a small tweak. As it stands, if do something > like > > $ MAX=5; DIVISOR=3 > $ ceil("$MAX / $DIVISOR") > 1 > > bc will do the math but you'll get the wrong answer. bc's scale > defaults to 0, so an integer is returned by the division operation > and the ceiling of an integer is itself. Change ceil to > > function newceil () { echo "define ceil (x) {if (x<0) {return x/1} \ > else {if (scale(x)==0) {return x} else {return x/1 + 1 }}} ; \ > scale=1; y=$1; scale=0; ceil(y)"  bc; } > > and you can give it a tasty arithmetic expression: > > $ MAX=5; DIVISOR=3 > $ newceil("$MAX / $DIVISOR") > 2 > > Quotes are necessary to make it all one argument; you might be able to > get around this by using $* instead of $1 in the function, but I haven't > tested that, so be careful. Even as it stands there may be weird edge > cases I haven't thought about. > > Don't trust something like this with user input that hasn't been > sanitized, but that's good practice for shell scripts in general. > > Paul > ___________________________________________________________________________ > Philadelphia Linux Users Group  http://www.phillylinux.org > Announcements  http://lists.phillylinux.org/mailman/listinfo/plugannounce > General Discussion  http://lists.phillylinux.org/mailman/listinfo/plug >  J. ___________________________________________________________________________ Philadelphia Linux Users Group  http://www.phillylinux.org Announcements  http://lists.phillylinux.org/mailman/listinfo/plugannounce General Discussion  http://lists.phillylinux.org/mailman/listinfo/plug

