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> This belittles their and anyone else's bash scripts for git as 'toys'. They often make great toys in the sense that toys are fun but it's harder to build rob

• falsedan 9y ago
  > They often make great toys in the sense that toys are fun but it's harder to build robust things in bash scripts. Programming is hard, regardless. You're being very dismissive towards shell scripters, and it comes off as elitist. > But where bash scripts fall down is the constant re-parsing of text, data has to be passed through the kernel, and extra processes (when you use xargs, which tends to happen for complicated tasks.) This adds up super quick. What do you mean by parsing? Copying, reading? The buffers sit in kernel memory, sure… but that's pretty fast if every line in your program is concurrent. > xargs Did you have a bad experience with xargs? > extra processes Did you have a bad experience with… running out of… PIDs? > > Casting bash as the insane bad language > I never said that You implied it by calling a non-bash language 'sane'; thus, bash must be insane. > I didn't recommend C Your blanket recommendation of 'anything but bash' did. I feel that sometimes you need to have more context of a situation before dictating a course of action that must be followed.
  • jacobparker 9y ago
    > Programming is hard, regardless. You're being very dismissive towards shell scripters, and it comes off as elitist. I think you're taking this too personally. I write _a lot_ of bash scripts and like bash (as I've already indicated.) It's not always the right tool for the right job (no tool is...) > What do you mean by parsing? Copying, reading? The buffers sit in kernel memory, sure… but that's pretty fast if every line in your program is concurrent. The buffers don't just sit in the kernel, they are copied between processes (via write/read.) This involves many many context switches. By contrast (but this is just an example), libgit2 will hopefully mmap your packfiles, and once the data is mapped in you don't have to leave your process. Parsing is sometimes obvious, for example multiple passes over the data with grep and sed to shape it the way you want. It's true that components of the pipeline can run in parallel but the problem is they do a lot of unnecessary work - parallelizing unnecessary work doesn't remove it and once you hit the limit of # of cores (which is very relevant when generating HTML - something often done by webservers with many concurrent requests where you don't have cores to spare on parallelizing inefficient algorithms.) Parsing is sometime not as obvious, for example steps in the pipeline doing redundant Unicode validation. This is an artifact of squeezing things through read/write with reusable components. It's convenient (which makes it great for prototyping, or for things that "don't matter") but this adds up to poor performance. > Did you have a bad experience with xargs? > Did you have a bad experience with… running out of… PIDs? I think you're being very uncivil. xargs is useful but it (with the common options like -n and -P) can spawn many processes which has a tremendous overhead vs an alternative like a function call. It's purely a performance thing. (I probably should be using parallel but I'm used to xargs :( )
    • falsedan 9y ago
      > I think you're being very uncivil. I'm sorry. I see how my questions come off as questioning your experience, and I didn't mean to do that. > I think you're taking this too personally. I think your reluctance to admit that you needlessly insulted some class of devs is exclusionary. Casual readers of these comments may think it's bad to write bash, or that it's ok to bash people who do. > The buffers don't just sit in the kernel, they are copied between processes (via write/read.) Yes, that's right. I know how pipes work, thanks. What you call 'parsing' I would call processing. Parsing has a well-defined meaning in the context of computer science: turning tokens into a data structure (like a syntax tree). > parallelizing unnecessary work doesn't remove it Is unnecessary work a problem? If you're being charged by the second, perhaps it may be cost-effective to eliminate it… but most of the time, developer productivity is a bigger cost. I see that you are mindful of the performance implication of your code. I usually have to think of developer throughput, so I'm very tolerant of inefficient use of hardware if it means someone gets their job done faster.
• kbenson 9y ago
  > But where bash scripts fall down is the constant re-parsing of text, data has to be passed through the kernel, and extra processes (when you use xargs, which tends to happen for complicated tasks.) This adds up super quick. You do't always have to use xargs. There are many ways to pipeline shell scripts. For one, you can process the input stream and add markers to make it easier to identify items later in the stream, or convert it to a well defined format for a similar outcome. Additionally, any extra resource and time usage from xargs parsing arguments (which I think is likely very small), can probably be easily recouped by the fact that you can use a single xargs flag to run commands in parallel. I've effectively used xargs to automate connecting to through SSH and running commands on hundreds of servers when automating processes. Finally, you're setting up a false dichotomy between shell pipelines and programming. I work in Perl for my day job, and write complex, well structured and designed Perl in that job. I also write shell scripts and Perl one liners. More importantly, I often use the Perl I've written in my one liners by loading the module and calling the functions I've defined there. In this way I get the best of both worlds, where I get to use pipelines to quickly munge text, and then pass it to more complex well written routines to process. This can often be parallelized as well.