2023年3月22日(水) 6:00 Greg Wooledge <g...@wooledge.org>: > I don't use programmable completion, but I could *imagine* someone using > a temp file to store the results, then using mapfile to read them back > in, to avoid the fork() that the command substitution uses.
I wouldn't say my usage is typical, but I do that in fact. I have a shell function to do that for an arbitrary command (which I once posted in help-bash [1] but now it's old. The latest is [2]) and use it everywhere. [1] https://lists.gnu.org/archive/html/help-bash/2020-05/msg00057.html [2] https://github.com/akinomyoga/ble.sh/blob/2eadcd5b/src/util.sh#L2173-L2225 > You'd > need a non-forking way to create the temp file, and to remove it, though, > or you'll lose all your gains in those steps. Yes, there is no gain for the temp file If we are going to do that only once. But if we are going to use it repeatedly in one interactive session or in a single execution of a Bash program, we can obtain gains because we can create the temporary file only once at the beginning of the session/program (of course with appropriate permissions, etc.). Of course, the temporary file should be cleaned up later by using the EXIT trap or another way. [3] https://github.com/akinomyoga/ble.sh/blob/2eadcd5b/ble.pp#L1346-L1486 (creation of a tempdir) [4] https://github.com/akinomyoga/ble.sh/blob/2eadcd5b/ble.pp#L1501-L1551 (cleanup) ---- But I also sometimes utilize `compgen' for purposes unrelated to completions. For example, when I want to check the list of Bash versions installed in my system, I would directly run $ compgen -c bash in the command line. Another usage is to filter array elements by « compgen -W '"${arr[@]}"' -X '...' » (assuming the array elements do not contain newlines), which can be combined with the temporary-file the approach mentioned above. -- Koichi
