Favor single quote's where possible

[oliv3r]

For new checks and feature suggestions

• https://www.shellcheck.net/ (i.e. the latest commit) currently gives no useful warnings about this
• I searched through https://github.com/koalaman/shellcheck/issues and didn't find anything related

I've been a 'double quote' guy for all my live, as C says, a string is surrounded by double quotes' ;) Single quotes are for characters! However in shell, this is not true. As most, I was stubborn and used double quotes whenever anyway ;)

After years, I've come to the realization, from a safety/security point of view, it actually does make sense to favor single quotes in scripts. It indicates 'no processing/expansion on the content of this string shall be done' (right?). As such, the choice (recommendation) should be, that whenever a variable does not contain anything that ought to be processed, favor single quotes.

Linters for example, such as pep8 also do this afaik as well.

[brother]

As such, the choice (recommendation) should be, that whenever a variable does not contain
anything that ought to be processed, favor single quotes.

(bash)

echo 'big up'
myvar='hello'

# rather than

echo "I know my BGP"
myothervar="world"

# and be careful with processing

echo "$myvar $myothervar"
echo '$myvar $myothervar'

Interesting to see if there are data from the big set @koalaman uses for testing that would indicate that this would be a good choice. For my own code I think I more often have processing involved and mostly need to avoid spacing issues and so on. But I haven't looked.

[koalaman]

This is a pretty subjective style debate that it doesn't make sense for ShellCheck to pick sides in, but it could potentially be an explicitly enabled optional suggestion.

[felipecrs]

+1 to be an optional rule, preferably with "Did you mean" suggestions so that it can be auto-fixed with VS Code ShellCheck on save.

[oliv3r]

@koalaman mostly true and I agree, as an optional it makes a lot of sense.

A bit off-topiic, but speaking of optional's, could you do something like enable="all !favor_single_quotes" for example?

[felipecrs]

Or:

enable=all
disable=favor-single-quotes

[oliv3r]

Ah yeah, that looks good to me too.

[felipecrs]

I changed my mind, I think this should be an optional rule just like prefer-double-brackets. :-P

[oliv3r]

haha, but all enables all optionals no? or is it

enable=all, prefer-double-brackets

cause that's kind of weird :p

[felipecrs]

Lol

You are absolutely right. I confused myself. :-)

[ramses0]

Please see the linked issue #2687 ... I believe a strong case can be made that ' should be preferred for as many strings as possible. Similar preferences and reasoning can be found in other linters (eg: https://eslint.org/docs/latest/rules/quotes ):

"""Object option:

"avoidEscape": true allows strings to use single-quotes or double-quotes so long as the string contains a quote that would have to be escaped otherwise"""

[oliv3r]

BTW, we already have the opposite in SC2016 :)

[ramses0]

@oliv3r - is this then just a matter of "patches welcome"?

[oliv3r]

@ramses0 I don't know? That's up to the maintainer; but I would expect it to be so?