12 Nisan 2021 Pazartesi tarihinde David A. Wheeler <dwhee...@dwheeler.com> yazdı:
> > > On Apr 12, 2021, at 10:57 AM, Oğuz <oguzismailuy...@gmail.com> wrote: > 12 Nisan 2021 Pazartesi tarihinde David A. Wheeler via austin-group-l at > The Open Group <austin-group-l@opengroup.org> yazdı: >> >> If you want a robust shell script, I recommend that you try out the tool >> “shellcheck”. >> That checks a shell script against a set of recommended practices (e.g., >> use “$variable” not $variable). >> > > If it makes that suggestion no matter what context `$variable' is used in, > I don't see how it'll help make a shell script "robust”. > > > It’s very common advice to recommend using double-quotes on variable > expansions unless you > have a *good* reason to do otherwise in shell scripts, because it prevents > word splitting > on a variable reference, and in most cases you do NOT want the word > splitting. Examples: > * For example, the "Advanced Bash-Scripting Guide” says, > “When referencing a variable, it is generally advisable to enclose its > name in double quotes.” > https://tldp.org/LDP/abs/html/quotingvar.html > * The “Quotes” page says: > "When in doubt, double-quote every expansion in your shell commands.” > https://mywiki.wooledge.org/Quotes#I.27m_Too_Lazy_to_Read. > 2C_Just_Tell_Me_What_to_Do > * https://www.tecmint.com/useful-tips-for-writing-bash-scripts-in-linux/ > * https://levelup.gitconnected.com/9-tips-for-writing-safer- > shell-scripts-b0c185da9bae#729e > Whether it is a common advice or not doesn't mean anything, people say stupid things on the internet all the time. > Yes, there are rare cases where you *do* want word-splitting. In those > cases, omit the double-quotes, > and shellcheck lets you disable checks in specific uses when you actually > *did* want this. > Huh, now I see what those `SC12345' comments in terribly written, barely working shell scripts mean. Following the rule “always double-quote unless you have special reasons” > means that you don’t have to do > program-wide analysis to think about word-splitting in most variable > references. > As a result, it tends to make creating *reliable* scripts easier. > I don't need a tool for reminding that to me. Taking "always double-quote your dollar variables", "eval is evil, avoid it", etc. as "the rule" is cargo cult programming. Average programmer's incompetence doesn't make the shell broken or unsafe or anything like that and doesn't justify parroting nonsensical advice like those. > > --- David A. Wheeler > > > -- Oğuz
