Re: Bash true/false builtings undocumented? "false" not working?
On Fri, Aug 17, 2018 at 06:46:54PM +1000, Zenaan Harkness wrote:
> 1)
> Bash man page largely fails to document the true and false builtins
> AFAICT, except for this sentence just under the heading
> "^SHELL BUILTIN COMMANDS":
>
> The :, true, false, and test builtins do not accept options and do
> not treat -- specially.
>
> But whilst the subsequent list of Bash builtin commands DOES include
> entries for ":" (the very first entry) and "test", it appears to fail
> to include entries for "true" and for "false".
>
> This would not matter so much except for the following:
>
>
> 2)
> Why is executing "false" prior to testing it's output, apparently
> differen to executing "false" in a pipeline, e.g.:
>
> $ false
> $ test $? && echo ok || echo error $?
> ok
> $ false blah
> $ test $? && echo ok || echo error $?
> ok
> $ false --
> $ test $? && echo ok || echo error $?
> ok
> $ true
> $ test $? && echo ok || echo error $?
> ok
> $ true && echo ok || echo error $?
> ok
> $ false && echo ok || echo error $?
> error 1
> $ false blah && echo ok || echo error $?
> error 1
> $ false 2 && echo ok || echo error $?
> error 1
> $ false -- && echo ok || echo error $?
> error 1
> $ builtin false -- && echo ok || echo error $?
> error 1
> $ builtin false --
> $ test $? && echo ok || echo error $?
> ok
> $ which false
> /bin/false
> $ /bin/false
> $ test $? && echo ok || echo error $?
> ok
>
>
>
> The above results are perplexing me, and frustratingly
> inconsistent!
>
> For example, "man false" says inter alia:
>
> NAME false - do nothing, unsuccessfully
> …
> DESCRIPTION Exit with a status code indicating failure.
>
>
> The descriptions suggests that /bin/false ought work outside of a
> pipeline in the same as way inside a pipeline - vhy, is, eet, not,
> so?
>
>
> TIA,
Could it be that the reason this does not work from the shell prompt
as I expect, is perhaps that my command prompt is successfully
running a command in between, and therefore hiding all error codes?
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