[Toybox] Testing: how to check return code (Rob Landley)

[Rob Landley]

On 11/6/19 3:34 AM, scsijon wrote:
> from the (matching) table in the wikka>
> 
> Exit Code Number    Meaning    Example    Comments
> 
> 1    Catchall for general errors    let "var1 = 1/0"    Miscellaneous errors,
> such as "divide by zero" and other impermissible operations

Not helpful.

> 2    Misuse of shell builtins (according to Bash documentation) empty_function()
> {}    Missing keyword or command, or permission problem (and diff return code on
> a failed binary file comparison).

We already know that "false" and "error" are sometimes distinguished by this,
but commands that _don't_ distinguish don't return 2 for error so it's not
generally useful.

> 126    Command invoked cannot execute    /dev/null    Permission problem or
> command is not an executable

So my guess was approximately right, but it's a bash-ism.

$ chmod +x PastedGraphic-2.png
$ ./PastedGraphic-2.png
./PastedGraphic-2.png: line 1: $'\211PNG\r': command not found
./PastedGraphic-2.png: line 2: $'\032': command not found
./PastedGraphic-2.png: line 3: syntax error near unexpected token `newline'
IHDR�4�k�
sRGB��
�
biTXtXML:com.adobe.xmp<x:xmpmeta xmlns:x="adobe:ns:meta/"
x:xmptk="XMP Core 5.4.0">'
$ echo $?
2

And on top of that, it's _fundamentally_ useless.

> 127    "command not found"    illegal_command    Possible problem with $PATH or
> a typo

Yes, I knew that.

> 128    Invalid argument to exit    exit 3.14159    exit takes only integer args
> in the range 0 - 255 (see first footnote)

Not usefull

> 128+n    Fatal error signal "n"    kill -9 $PPID of script    $? returns 137
> (128 + 9)

Already knew it.

> 130    Script terminated by Control-C    Ctl-C    Control-C is fatal error
> signal 2, (130 = 128 + 2, see above)

Not useful _and_ already knew it.

> 255*    Exit status out of range    exit -1    exit takes only integer args in
> the range 0 - 255

Should basically never happen.

> (sorry for the format, but that's the way it copied)

It's neither a standard, nor particularly helpful.

It's nice that this 20 year old document is in a wiki now, but it hasn't changed
since then and the bash scripting guide is documenting bashisms from the 2.x
era, which I'm already examining while doing shell stuff.

Rob