On Wed, 2010-06-30 at 23:56 +0200, Thomas Bächler wrote: > Am 30.06.2010 23:47, schrieb Victor Lowther: > > It is worth 10 - 30% speedup whenever you want to compare something. > > Where do you get this from? I always used [ ], and I found it > sufficient. Why is [[ ]] faster? [[ ]] is faster because it is bash syntax, not a builtin command like [ is. In most programs, both are fast enough, but you an see the difference if you run otherwise identical tests in a loop one million times. > > > -if [ "$USECOLOR" = "YES" -o "$USECOLOR" = "yes" ]; then > > +if [[ $USECOLOR = YES || $USECOLOR = yes ]]; then > > Why do you get rid of the quoting here? Quoting is nice. Because [[ ]] is bash syntax instead if a builtin comand, it relaxes the usual expansion rules -- inside of [[ ]], word splitting and pathname expansion are not performed, so you only have to quote strings if they need to be single-quoted. http://wiki.bash-hackers.org/syntax/ccmd/conditional_expression has more info. -- Victor Lowther LPIC2 UCP RHCE
