3 ms·

plan 9 who is a 3 line shell script that just greps the output of ps and sorts it. You could eliminate ps and just grep through /proc but why reinvent the wheel

plan 9 who is a 3 line shell script that just greps the output of ps and sorts it. You could eliminate ps and just grep through /proc but why reinvent the wheel when an existing tool already does part of the job? I see some comments here citing a lack of options, most of which appear to have nothing to do with who is logged into the machine.

fizzled 6y ago
Is /proc as portable as `ps`?
- hibbelig 6y ago
  I guess that Linux `/proc` is different from Plan 9 `/proc`, and Linux `ps` is different from Plan 9 `ps`. So maybe yes.
- JdeBP 6y ago
  There's a long explanation when it comes to ps, but the very short answer is twofold: * Don't parse the output of ps, unless it is my ps command (or plan 9's one, as here). See https://unix.stackexchange.com/a/593198/5132 https://unix.stackexchange.com/a/593198/5132 and https://unix.stackexchange.com/a/578816/5132 https://unix.stackexchange.com/a/578816/5132 , and their further reading, especially Greg Wooledge's article. * /proc is as portable as ps, but that doesn't really amount to much because neither is really portable at all. Pretty much every operating system's /proc is different; and no implementation of the ps command fully conforms to even the limited subset laid out in the Single Unix Specification.
deleted 6y ago
[deleted]
forgotpwd16 6y ago
Source for the mentioned script: https://github.com/0intro/plan9/blob/master/rc/bin/who https://github.com/0intro/plan9/blob/master/rc/bin/who. Also, other utilities implemented as scripts are fshalt (P9's shutdown), kill, lookman (P9's apropos), uptime and whois.
- jf 6y ago
  Does anybody know why there are line breaks in the sed command?
  - deleted 6y ago
    [deleted]
  - forgotpwd16 6y ago
    It runs multiple expressions. That is sed '/pattern1/d pattern2/d' is the same with sed '/pattern1/d; /pattern2/d' and sed -e '/pattern1/d' -e '/pattern2/d' I believe those are portable across all `sed` implementations, and they at least work with GNU `sed --posix` and plan9port's sed.
    - jf 6y ago
      Thank you! This is exactly the kind of reply I was hoping for.

fizzled 6y ago

Is /proc as portable as `ps`?

hibbelig 6y ago
I guess that Linux `/proc` is different from Plan 9 `/proc`, and Linux `ps` is different from Plan 9 `ps`. So maybe yes.
JdeBP 6y ago
There's a long explanation when it comes to ps, but the very short answer is twofold: * Don't parse the output of ps, unless it is my ps command (or plan 9's one, as here). See https://unix.stackexchange.com/a/593198/5132 https://unix.stackexchange.com/a/593198/5132 and https://unix.stackexchange.com/a/578816/5132 https://unix.stackexchange.com/a/578816/5132 , and their further reading, especially Greg Wooledge's article. * /proc is as portable as ps, but that doesn't really amount to much because neither is really portable at all. Pretty much every operating system's /proc is different; and no implementation of the ps command fully conforms to even the limited subset laid out in the Single Unix Specification.

deleted 6y ago

[deleted]

forgotpwd16 6y ago

Source for the mentioned script: https://github.com/0intro/plan9/blob/master/rc/bin/who https://github.com/0intro/plan9/blob/master/rc/bin/who. Also, other utilities implemented as scripts are fshalt (P9's shutdown), kill, lookman (P9's apropos), uptime and whois.

jf 6y ago
Does anybody know why there are line breaks in the sed command?
- deleted 6y ago
  [deleted]
- forgotpwd16 6y ago
  It runs multiple expressions. That is sed '/pattern1/d pattern2/d' is the same with sed '/pattern1/d; /pattern2/d' and sed -e '/pattern1/d' -e '/pattern2/d' I believe those are portable across all `sed` implementations, and they at least work with GNU `sed --posix` and plan9port's sed.
  - jf 6y ago
    Thank you! This is exactly the kind of reply I was hoping for.