On Sun, Dec 11, 2022 at 08:54:27AM -0500, Greg Wooledge wrote:
> On Sun, Dec 11, 2022 at 08:16:35AM +0100, tomas@tuxteam.de wrote:
> > That said. Greg, I was also shaken by your roaring tone.
>
> Yeah, well, he was told the same thing, repeatedly, by multiple people,
> and somehow he managed to ignore every single instance of it.
>
> It's rather frustrating.
I understand. Still yelling at people detracts from your extremely
valuable contributions here.
I would consider myself as a reasonably experienced shell programmer,
and still learn from you time and again, so thanks for this.
> As a formal statement for anyone else who's reading this, who might
> actually listen:
>
>
> echo ${TEST} does NOT show the contents of the TEST variable reliably.
>
>
> For the following reasons:
>
> 1) ${TEST} is not a substitute for "$TEST". They do not mean the same
> thing. You MUST double-quote the variable when you expand it, or
> else the contents will undergo word splitting and pathname expansions.
>
> There are specific cases where the double-quotes may be omitted, but
> until you know what those cases are, it's best to use the quotes
> every time. This is not one of those cases.
To illustrate: in my home directory
tomas@trotzki:~$ FOO='key* hi* ho*'
tomas@trotzki:~$ echo ${FOO}
=> keys.out keys1.out hill.scad holidays hours
Needles to say: in your home directory, results may be different :)
> 2) echo may interpret the content of TEST as an option (-n or -e), or it
> may interpret backslash sequences inside the content, depending on
> which shell you're using, and which platform you're on.
>
> The use of echo with variable arguments is therefore strongly
> discouraged.
Again, illustration:
tomas@tritzki:~$ TEST="-n o n o"
tomas@trotzki:~$ echo ${TEST}
=> o n o
(with no newline at its end)
> 3) echo usually, but not always, adds an additional newline character to
> the output. In most cases, this is acceptable, even preferable. But
> when the OP is complaining of an "extra CR/LF" [sic], but is using
> echo to produce the extra newline himself, well... there you have it.
Now which cases, besides when the -n option is given (I don't know,
off the bat, I must admit).
(more useful advice)
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