On 2022-06-12 at 07:57, rhkramer@gmail.com wrote: > On Saturday, June 11, 2022 10:25:34 AM Greg Wooledge wrote: > >> On Sat, Jun 11, 2022 at 09:54:17AM -0400, rhkramer@gmail.com >> wrote: >>> eval `ssh-agent` > >> For the record, the command you've got here is written in a very >> antiquated way. A better (as well as more modern) way to write it >> would be: >> >> eval "$(ssh-agent)" > > I am curious about the origin of the more modern syntax -- was it > driven (or partially driven) by the possiblity of (a human) confusing > the backticks for single quotes (like I did)? I don't know the history myself (a brother of mine might, but I don't know if he's up at this hour), but my guess would be more that it's about other things - such as, for example, nesting. The syntax (modulo quoting) $ foo $(bar $(baz)) is unambiguous, but the syntax $ foo `bar `baz`` is sufficiently ambiguous that it's not going to practically be possible for the shell to determine what the writer intended to do. There's a possibility that something like $ foo `bar \`baz\`` might be supported and might work, but even if so, that would just mean having to keep track of how many escaping backslashes you've used on each backtick - and it would probably make managing quoting the subshells even harder to get right. It'd be unwieldy at best, compared to the explicit start-and-end markers that are involved with the $() syntax. -- The Wanderer The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man. -- George Bernard Shaw
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