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Great post, you are wise in the ways of the shell. Minutiae like this is exactly why I stop writing shell scripts the moment I start, and reach for python or so

Great post, you are wise in the ways of the shell. Minutiae like this is exactly why I stop writing shell scripts the moment I start, and reach for python or some other sane language. But, I can't help but respect when I see masters of sh work their magic.

dundarious 4y ago
Honestly, 90% of problems with scripts are people forgetting to put double quotes around stuff. The other stuff doesn't come up that much, and once you write a few decent scripts, the other stuff is as easy as noticing someone wrote `open = True` in Python, not realizing they've redefined a builtin function, and the fix is just do `is_open = True`. So just put double quotes around all your variable expansions unless you know you shouldn't -- 90% of scripts would be "fixed" with just that. And don't bother putting curly braces into the variable expansion unless you know you need to. People tend to think `echo ${s}` is somehow better than `echo $s` when it's exactly the same -- the curly braces are just a way to allow you to, e.g., write `"${s}_"` as distinct from `"${s_}"`. AFAIK in fish `${s}` is identical to `"$s"`, but that's a different kettle of sh.
xelxebar 4y ago
Try enabling shellcheck linting in your editor! It would immediately warn about unquoted variable expansions and the like. For the vast majority of "gotchas" shellcheck will prod you in the right direction. That said, to write good shell scripts requires actually learning the shell paradigm, instead of just trying to write "Python with Shell syntax".
wolletd 4y ago
I think there's place for both. When I build software installers for our embedded systems, the "frontend" tools production uses are written in a "sane" language, but the actual installation of software and configuration of the systems is done in shell. Because for running a bunch of apt/tar/cp/ln/sed commands to configure a Linux machine, it is the sane language.

dundarious 4y ago

Honestly, 90% of problems with scripts are people forgetting to put double quotes around stuff. The other stuff doesn't come up that much, and once you write a few decent scripts, the other stuff is as easy as noticing someone wrote `open = True` in Python, not realizing they've redefined a builtin function, and the fix is just do `is_open = True`. So just put double quotes around all your variable expansions unless you know you shouldn't -- 90% of scripts would be "fixed" with just that. And don't bother putting curly braces into the variable expansion unless you know you need to. People tend to think `echo ${s}` is somehow better than `echo $s` when it's exactly the same -- the curly braces are just a way to allow you to, e.g., write `"${s}_"` as distinct from `"${s_}"`. AFAIK in fish `${s}` is identical to `"$s"`, but that's a different kettle of sh.

xelxebar 4y ago

Try enabling shellcheck linting in your editor! It would immediately warn about unquoted variable expansions and the like. For the vast majority of "gotchas" shellcheck will prod you in the right direction. That said, to write good shell scripts requires actually learning the shell paradigm, instead of just trying to write "Python with Shell syntax".

wolletd 4y ago

I think there's place for both. When I build software installers for our embedded systems, the "frontend" tools production uses are written in a "sane" language, but the actual installation of software and configuration of the systems is done in shell. Because for running a bunch of apt/tar/cp/ln/sed commands to configure a Linux machine, it is the sane language.