Nicolas Bonifas wrote: >> > I don't know much about bash internals, but there is probably room for >> > a huge performance improvement in speeding up the eval builtin. >> > What do you think about it? Would it be a difficult task? >> >> It is more likely to be the command substitution that is slow. > > You're right: > $ time (echo `dircolors` > /dev/null) > > real 0m0.318s > user 0m0.312s > sys 0m0.008s > > I ran the previous tests with bash-3.1. With bash-3.2, echo > `dircolors` take 0.088s of user time (1/4th of the time needed by > bash-3.1), and dircolors > dircolors_output && sh ./dircolors_output > still takes 0.004s, so it is more than 20 times faster than using > command substitution. > > So, do you think that speeding up command substitution would be a > difficult task?
I assume you know that the speed issues most likely come from the operating system's supporting functions like the fork() and exec*() family members? Executing another process takes time and there is not much you can do about it. If you have speed problems while using a huge amount of command substitutions you either have a bad script design or use the wrong language for your specific task IMHO. J.
