Re: [PATCH] Catch errors properly, if whoami or who don't exist

Stefan wrote:
> [...]
>
>>>> In fact, how are you even running the dejagnu(1) and runtest(1) 
>>>> scripts if /bin/sh does not exist?  Their #! lines refer to /bin/sh...
>
> In Guix there is an automatism to patch (only) all shebangs to the 
> correct absolute paths.

So you patch every script instead of installing symlinks that allow 
interpreters to be easily updated...

> If you search for “ sh ” usage across the DejaGnu source, then you 
> will find plenty of places happily using sh without /bin/.  But there 
> is only this one usage of /bin/sh.  So for consistency one might argue 
> to change it.

A search of the source tree for " sh " finds exactly three code files in 
DejaGnu containing that word:  lib/remote.exp, lib/rsh.exp, and 
lib/ssh.exp.  Other files are either documentation or imported.  
Notably, config.sub is actually matching the string "sh" in a case block 
and configure only references " sh " while attempting to determine the 
PATH_SEPARATOR (in a test that assumes that /bin exists, notably) and in 
a list of names under which a POSIX shell might be found.

>>> POSIX says otherwise, you must not rely on the presence of /bin/sh; 
>>> cf. 
>>> <https://pubs.opengroup.org/onlinepubs/9799919799/utilities/sh.html#tag_20_110_16>. 
>>> The path to the interpreter can be easily substituted e.g. with 
>>> autoconf.
>
>> That is in an informative section; and it is indeed correct that 
>> /bin/sh cannot be assumed to be a POSIX shell.  The scripts that use 
>> #!/bin/sh in DejaGnu avoid making such an assumption.  That section 
>> also says that you are supposed to be able to find a POSIX shell with 
>> `command -v sh` but I suspect that Autoconf does considerably more 
>> work than that to locate a suitable shell. 
>
> There is also confstr()¹, which is able to deliver a PATH, which is 
> guaranteed to find sh.  And there is also a hint to “popen("command -p 
> getconf variable", "r");”

Will `command -v sh` reliably locate a POSIX sh?

A quick test at cfarm111 finds that AIX7.1 command(1) does not allow the 
combination of -p and -v, although `getconf PATH` works and is defined 
to return the _CS_PATH string (see 
<URL:https://pubs.opengroup.org/onlinepubs/9699919799/utilities/getconf.html#tag_20_53_05>) 
available to C programs using confstr().  Remember that dejagnu(1) is a 
shell script, so the XCU volume of the POSIX spec is relevant, not 
(confusingly) XSH.


-- Jacob