đ Budi reacted via Gmail <https://www.google.com/gmail/about/?utm_source=gmail-in-product&utm_medium=et&utm_campaign=emojireactionemail#app>
On Sun, Dec 22, 2024 at 10:45âŻAM Martin D Kealey <mar...@kurahaupo.gen.nz> wrote: > > On Sun, 22 Dec 2024, 03:49 Budi, <budikus...@gmail.com> wrote: > >> How is Bash' code to store string of any characters should be containing >> pair of "" and '' at the same time explicitly, being exact verbatim so, >> ie. cannot be modified, escaped or etc, as expected from ordinary/naive >> human writing), into a variable >> > > Any expectation that literal text can be written exactly verbatim (only > adding fixed delimiters before and after) is unrealistic. We can't even do > that in human languages, so doing that in a language intended for computers > to read would make it very hard for humans to write. > > If you can abandon that assumption then Greg's answer is quite > comprehensive. > > But a nagging question is why does the text contain both ' and " > characters? Is it written in a human language or a computer language? > > If it's a human language, consider using âtypographicâ âquotesâ instead of > the much-overloaded ASCII " and ' characters. > > If it contains shell script fragments, then consider not storing code in > variables in the first place, but using something more appropriate such as > functions. > > If it absolutely has to store shell code in variables, consider arranging > the code in question so that it only uses one kind of quote mark, and use > the other kind to delimit that. > > Failing that, by far the "simplest" approach to "literal" text is not to > have it inside the script, but in a separate file that the script can read. > > to insert \ in front of EVERY character, and NOT use any surrounding > quotes at all. Of course, this looks REALLY ugly and hard to read, but it's > very easy to think about when you're WRITING. > > Let's say you want this: > > let's put "this" text worth $1 in a variable > > This becomes: > > phrase=\l\e\t\'\s\ \p\u\t\ \"\t\h\i\s\"\ \t\e\x\t\ \w\o\r\t\h\ \$\1\ > \i\n\ \a\ \v\a\r\i\a\b\l\e > > If you don't mind a little bit of thinking, you can skip the \ before > alphanumeric characters, leaving: > > phrase=let\'s\ put\ \"this\"\ text\ worth\ \$1\ in\ a\ variable > > If you don't mind even more thinking then you can instead memorize the > list of characters that need \ and skip all the others; they are space, > tab, newline, and "#$'&<>*()?`\[]| > > Importantly \ itself is in that list. Each round of encoding will (at > least) double the number of \ present; $foo -> \$foo -> \\\$foo -> > \\\\\\\$foo etc. > > >7 tries to no avail.. so help out solve >> > > Using $( echo ⌠) partially undoes some of the encoding, so it's actively > counterproductive to this task. > > "Guessing" when there are infinite possibilities is pointless; knowledge > of other programming languages will lead you *away* from what you need to > know, not towards it. > > You should *not* expect the code that embodies your text to look *exactly* > like the text unless it's very simple; it will almost always need > modifications. Stop thinking in terms of "quoting", and instead think in > terms of "encoding". > > If you want to assign something to a variable, start by looking up > "assignment" in the manual. It says that an assignment looks like > > NAME=WORD > > The fact that NAME and WORD are upper-case is important: it means they > have meanings that are defined elsewhere in the manual. > > NAME is easy: any sequence of alphanumeric characters plus underscore, as > long as it doesn't start with a digit. > > WORD is more complicated, but the important point is that it *ends* just > before the first *unquoted* whitespace or shell metacharacter. It does > *NOT* say that it end at a "closing quote". > > Let me say that again, because it's critically important. The WORD that is > assigned to the variable does *NOT* end just because there's a closing > quote. It continues until just before whitespace or one of ();<>&| > > Let that sink in for a bit. > Quotes can be opened and closed multiple times within a single WORD. > Different parts of a single WORD can be unquoted, or quoted in one of 4 > different ways. > > All of this is just one assignment: > > this_is_a_NAME='everything after the = is a valid WORD, and this part of > it is in single quotes 'this-part-is-unquoted" this part is in double > quotes"$' this part is in special quotes 'and\ the\ spaces\ in\ this\ part\ > are\ escaped\ with\ \ backslashes', which counts as a form of quoting'. > > -Martin > >>
