Ahh, really sorry - just reminded something. With "…" notation you can’t copy and paste strings with not escaped " character. I was interested in << EOL … EOL syntactic sugar, because you can set prefix and suffix on yourself.
Eiji
0
NobbZ
Then use single quotes.
The user has to choose the appropriate quotes anyway. If they don’t use bash but eg fish the shell might behave different from your documentation/examples. Therefore it’s best to only document the meaning of the named/positional argument in an executable.
2
alco
I see. So the question is not about Elixir at all, it’s about passing multiple lines as a single positional argument to a program when running it in a shell.
The common practice is to use quotes like NobbZ has suggested. You could use shell substitution but that would look rather weird:
$ elixir -e "IO.inspect System.argv" -- --test $(cat <<EOL
bar
baz)
EOL
)
["--test", "bar", "baz)"]
# Must use quotes around the shell substitution
$ elixir -e "IO.inspect System.argv" -- --test "$(cat <<EOL
"bar"
baz)
EOL
)"
["--test", "\"bar\"\nbaz)"]
2
Eiji
It’s definitely best answer! With it everything could be passed and automatically escaped without any worry. End-user could decide when to stop adding text pretty easy and there is no need to change code.
I just wonder why it’s not possible to do it directly (not inside $() - command substitution) like cat could.
0
NobbZ
cat does read from stdin if no filename is provided as positional argument. It also reads from stdin if - is given as a filename.
2
Eiji
Yeah, but it also does not freezes when there is nothing on stdin, right? I do not see any equivalent in Elixir documentation (maybe I have missed something). I though about doing it in with Task timeout, but then I was not sure what timeout should I use (assuming that you don’t know how much data is in stdin), so everything goes to point where I would like to check
last_arg = List.last(args)
all_args = case do
option_type(last_arg) != :string -> args
is_stdin_empty() -> raise "Missing #{last_arg} option value!"
true -> args ++ [read_stdin()]
end
defp option_type("--test"), do: :string
defp option_type(_option), do: :value
0
NobbZ
It will wait for input until it reads EOF. Try cat as a single command without anything else. It will not exit, but wait for you to provide input on stdin.
1
Eiji
oops, my bad - cat here is like IO.read(:line) in loop
So there is no way to check if stdin is empty for any language, right?
0
NobbZ
You will never know if stdin was empty or not before you received an end of file, and after that you can check for emptyness by simply counting bytes. That works in any language.
2
Eiji
ok, looks like I got it
So the best (to not cause confusion - look that cat does not say anything) way without hacks is printing some text like:
./example --test
[debug] Reading stdin for argument '--test'. In case you forgot to give it you can type it now. When you done please press '<ctrl>' + '<d>' in order to continue.
some
multiline
text here <ctrl>+<d>
["--test", "some\nmultiline\ntext here"]
Unfortunately even if there would be already << EOF … EOF argument value it looks like that’s not possible to handle it separately (to not print debug message in such case).
0