3 ms·

Fork performance is a much more severe problem on Windows (WSL1, MSYS2, etc.) than Linux, so I'm not claiming you'll personally run into it per se, but it can a

Fork performance is a much more severe problem on Windows (WSL1, MSYS2, etc.) than Linux, so I'm not claiming you'll personally run into it per se, but it can affect users of some scripts. But: performance was just one of the problems I cited. I gave you more than that -- one was a correctness reason (which you do care about) and had nothing to do with performance. And, again, incorrect buffering (which can make the script literally unusable in some cases) was just one example. I've seen needless redirection interfere with Ctrl+C handling too, though I don't recall the exact example. Oh, and there's terminal coloring and ANSI escape processing too, which programs detect differently. Point is, being unable to see the end of the pipe can definitely cause an unnecessary mess in some cases. As for readability - honestly, part of the reason you find it less readable is that you're missing something else. Namely, this: sed -e 's/pattern/replacement/g' -e 's/reallybigolhonkinpattern/other-replacement/g' wrongfile.conf | tr... | while read line; do... should really have been: sed -e 's/pattern/replacement/g' -e 's/reallybigolhonkinpattern/other-replacement/g' -- wrongfile.conf | tr... | while read line; do... which is in fact both more correct (at least when the file name isn't hard-coded, which is the common case in shell scripts) and more readable than your example; you can immediately spot where the file name is. The difference between that and cat "$blah" | sed ... is very minor at that point (and in fact you should be doing cat -- "$blah" as well...); anybody reading a command like sed without a pipe input knows to look for an input argument. The important point regarding readability here is, it's not like the code gets overly tricky if you write it one way vs. another way. It's just a matter of spending 1-2 extra seconds glancing over. So it's very much a minor thing to be prioritizing above everything else. (If the logic became harder to reason about, that'd be a different story, and it'd put more weight on the readability aspect.)

thaumaturgy 3y ago
It's unclear if you missed the filename being wrongfile.conf. Embedding a -- in the middle of a long series of arguments isn't the magic pixie dust that suddenly makes the filename argument stand out the way that it does when it's the very first argument in the pipe. Yes, I saw your other points, and I chose this example because it is an example drawn from real-world use where there is zero objective reason to wag a finger about "useless use of cat". Those other points are not relevant in this example, and piping a cat into some other commands into a while loop is pretty typical shellcode. Forcing me to move a filename argument into the middle of a long line for stylistic reasons should be obviously wrong. It is one case where shellcheck is over-reaching and being a nuisance rather than helping me catch errors. This has been argued better and to death already: https://stackoverflow.com/a/16619430 https://stackoverflow.com/a/16619430, http://oletange.blogspot.com/2013/10/useless-use-of-cat.html http://oletange.blogspot.com/2013/10/useless-use-of-cat.html, https://news.ycombinator.com/item?id=23341711 https://news.ycombinator.com/item?id=23341711, https://news.ycombinator.com/item?id=36116208 https://news.ycombinator.com/item?id=36116208, https://news.ycombinator.com/item?id=6367319 https://news.ycombinator.com/item?id=6367319, https://news.ycombinator.com/item?id=1116085 https://news.ycombinator.com/item?id=1116085, etc.
- dataflow 3y ago
  If you deliberately chose a specific example then you forgot what this discussion was about? You're giving an existence proof. Yes, there exist situations where it's fine. But this discussion was about what constitutes good habits, not about cherrypicked counterexamples. The whole point of paying attention to good and bad habits is that they sometimes make a difference, and if your habits are bad, you'll sometimes get yourself in trouble. And it's not like you can reasonably expect shellcheck to distinguish the benign cases from the potentially problematic ones either. It has to give you a recommendation about what constitutes good habits, and avoiding redundant calls to cat is a good habit for all the reasons I just listed, even if in some cherrypicked cases it provides ~no benefit.

thaumaturgy 3y ago

It's unclear if you missed the filename being wrongfile.conf. Embedding a -- in the middle of a long series of arguments isn't the magic pixie dust that suddenly makes the filename argument stand out the way that it does when it's the very first argument in the pipe. Yes, I saw your other points, and I chose this example because it is an example drawn from real-world use where there is zero objective reason to wag a finger about "useless use of cat". Those other points are not relevant in this example, and piping a cat into some other commands into a while loop is pretty typical shellcode. Forcing me to move a filename argument into the middle of a long line for stylistic reasons should be obviously wrong. It is one case where shellcheck is over-reaching and being a nuisance rather than helping me catch errors. This has been argued better and to death already: https://stackoverflow.com/a/16619430 https://stackoverflow.com/a/16619430, http://oletange.blogspot.com/2013/10/useless-use-of-cat.html http://oletange.blogspot.com/2013/10/useless-use-of-cat.html, https://news.ycombinator.com/item?id=23341711 https://news.ycombinator.com/item?id=23341711, https://news.ycombinator.com/item?id=36116208 https://news.ycombinator.com/item?id=36116208, https://news.ycombinator.com/item?id=6367319 https://news.ycombinator.com/item?id=6367319, https://news.ycombinator.com/item?id=1116085 https://news.ycombinator.com/item?id=1116085, etc.

dataflow 3y ago
If you deliberately chose a specific example then you forgot what this discussion was about? You're giving an existence proof. Yes, there exist situations where it's fine. But this discussion was about what constitutes good habits, not about cherrypicked counterexamples. The whole point of paying attention to good and bad habits is that they sometimes make a difference, and if your habits are bad, you'll sometimes get yourself in trouble. And it's not like you can reasonably expect shellcheck to distinguish the benign cases from the potentially problematic ones either. It has to give you a recommendation about what constitutes good habits, and avoiding redundant calls to cat is a good habit for all the reasons I just listed, even if in some cherrypicked cases it provides ~no benefit.