4 ms·

His "who" implementation is 73 lines (21 if you remove blank lines and comments). Compare that to 836 in GNU Coreutils[0]. [0] https://github.com/coreutils/cor

His "who" implementation is 73 lines (21 if you remove blank lines and comments). Compare that to 836 in GNU Coreutils[0]. [0] https://github.com/coreutils/coreutils/blob/master/src/who.c https://github.com/coreutils/coreutils/blob/master/src/who.c

BuildTheRobots 6y ago
> Of course, this only mocks the most basic features of the who command and doesn’t handle any option, like the famous `who am i` or `who mom hates`. it's not quite an apples to apples comparison as his rewrite doesn't handle any options or cleverness, but it's still a massive jump in LOC.
- eesmith 6y ago
  Nor is it anywhere near as portability. Though that's not a big issue these days.
  - chard_slicks_ 6y ago
    If you don't care about all the features then Busybox's implementation will work fine at 170 lines inclusive of comments.
  - eesmith 6y ago
    Wow, I touched a nerve I don't understand, to get a -1, so I'll explain myself. The GNU code looks like it's portable to a bunch of OSes, some with and some without a given feature. That sort of portability leads to having a lot of #ifdefs. If you're only going to support a handful of OSes - because that's all most people care about - then of course your code is going to be smaller. As a concrete example, the linked-to "who" uses: if (entry.ut_type != USER_PROCESS) continue; The GNU one uses: if (IS_USER_PROCESS (utmp_buf)) The IS_USER_PROCESS() macro is in gnulib's readutmp.h (which would need to be included in the overall line cound): # define IS_USER_PROCESS(U) \ (UT_USER (U)[0] \ && (UT_TYPE_USER_PROCESS (U) \ || (UT_TYPE_NOT_DEFINED && UT_TIME_MEMBER (U) != 0))) The UT_USER maps to ut_user on some systems, and ut_name on others: /* Accessor macro for the member named ut_user or ut_name. */ # if HAVE_UTMPX_H # if HAVE_STRUCT_UTMPX_UT_USER # define UT_USER(Utmp) ((Utmp)->ut_user) # endif # if HAVE_STRUCT_UTMPX_UT_NAME # undef UT_USER # define UT_USER(Utmp) ((Utmp)->ut_name) # endif This is because, as https://www.gnu.org/software/libc/manual/html_node/Logging-In-and-Out.html https://www.gnu.org/software/libc/manual/html_node/Logging-I... points out, "Note that the ut_user member of struct utmp is called ut_name in BSD. Therefore, ut_name is defined as an alias for ut_user in utmp.h" Each of those other macros supports cases where the machine supports a given test, and when it doesn't. Including for machines which don't implement ut_type! (That's what the UT_TYPE_NOT_DEFINED case is for, which falls back to using the time field ... which has its own set of variants!) Portability is neither options nor cleverness, so I added it to the list of considerations. But then again, most people now don't need to support decades of history and scores of Unix variants.
- chard_slicks_ 6y ago
  I know that it isn't a full implementation and my comment wasn't meant as a real comparison.
cat199 6y ago
openbsd 'who' is in the 300 range: http://cvsweb.openbsd.org/src/usr.bin/who/who.c?rev=1.29&content-type=text/x-cvsweb-markup http://cvsweb.openbsd.org/src/usr.bin/who/who.c?rev=1.29&con... this version appears to derive from rewriting unix who in the 4.4BSD era to replace AT&T code (copyright 1989 / no AT&T in header notes as basis for assumption)
- drewg123 6y ago
  Its interesting. FreeBSD's is about the same size, but was again re-written in 2002 to "to add some features required by SUSv3" : https://github.com/freebsd/freebsd/commit/1894db5ac7af64acc77acfbbc7b98c819dd70e22#diff-a4de903930ae110d2ca9604fd74b570f https://github.com/freebsd/freebsd/commit/1894db5ac7af64acc7...
MisterTea 6y ago
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.
kps 6y ago
V7 `who` was 62 lines; by V10 it was bloated up to 93.
alpb 6y ago
You'll like this Rob Pike thread https://twitter.com/rob_pike/status/966896123548872705 https://twitter.com/rob_pike/status/966896123548872705

BuildTheRobots 6y ago

> Of course, this only mocks the most basic features of the who command and doesn’t handle any option, like the famous `who am i` or `who mom hates`. it's not quite an apples to apples comparison as his rewrite doesn't handle any options or cleverness, but it's still a massive jump in LOC.

eesmith 6y ago
Nor is it anywhere near as portability. Though that's not a big issue these days.
- chard_slicks_ 6y ago
  If you don't care about all the features then Busybox's implementation will work fine at 170 lines inclusive of comments.
- eesmith 6y ago
  Wow, I touched a nerve I don't understand, to get a -1, so I'll explain myself. The GNU code looks like it's portable to a bunch of OSes, some with and some without a given feature. That sort of portability leads to having a lot of #ifdefs. If you're only going to support a handful of OSes - because that's all most people care about - then of course your code is going to be smaller. As a concrete example, the linked-to "who" uses: if (entry.ut_type != USER_PROCESS) continue; The GNU one uses: if (IS_USER_PROCESS (utmp_buf)) The IS_USER_PROCESS() macro is in gnulib's readutmp.h (which would need to be included in the overall line cound): # define IS_USER_PROCESS(U) \ (UT_USER (U)[0] \ && (UT_TYPE_USER_PROCESS (U) \ || (UT_TYPE_NOT_DEFINED && UT_TIME_MEMBER (U) != 0))) The UT_USER maps to ut_user on some systems, and ut_name on others: /* Accessor macro for the member named ut_user or ut_name. */ # if HAVE_UTMPX_H # if HAVE_STRUCT_UTMPX_UT_USER # define UT_USER(Utmp) ((Utmp)->ut_user) # endif # if HAVE_STRUCT_UTMPX_UT_NAME # undef UT_USER # define UT_USER(Utmp) ((Utmp)->ut_name) # endif This is because, as https://www.gnu.org/software/libc/manual/html_node/Logging-In-and-Out.html https://www.gnu.org/software/libc/manual/html_node/Logging-I... points out, "Note that the ut_user member of struct utmp is called ut_name in BSD. Therefore, ut_name is defined as an alias for ut_user in utmp.h" Each of those other macros supports cases where the machine supports a given test, and when it doesn't. Including for machines which don't implement ut_type! (That's what the UT_TYPE_NOT_DEFINED case is for, which falls back to using the time field ... which has its own set of variants!) Portability is neither options nor cleverness, so I added it to the list of considerations. But then again, most people now don't need to support decades of history and scores of Unix variants.
chard_slicks_ 6y ago
I know that it isn't a full implementation and my comment wasn't meant as a real comparison.

cat199 6y ago

openbsd 'who' is in the 300 range: http://cvsweb.openbsd.org/src/usr.bin/who/who.c?rev=1.29&content-type=text/x-cvsweb-markup http://cvsweb.openbsd.org/src/usr.bin/who/who.c?rev=1.29&con... this version appears to derive from rewriting unix who in the 4.4BSD era to replace AT&T code (copyright 1989 / no AT&T in header notes as basis for assumption)

drewg123 6y ago
Its interesting. FreeBSD's is about the same size, but was again re-written in 2002 to "to add some features required by SUSv3" : https://github.com/freebsd/freebsd/commit/1894db5ac7af64acc77acfbbc7b98c819dd70e22#diff-a4de903930ae110d2ca9604fd74b570f https://github.com/freebsd/freebsd/commit/1894db5ac7af64acc7...

MisterTea 6y ago

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.

kps 6y ago

V7 `who` was 62 lines; by V10 it was bloated up to 93.

alpb 6y ago

You'll like this Rob Pike thread https://twitter.com/rob_pike/status/966896123548872705 https://twitter.com/rob_pike/status/966896123548872705