Escape double quotes in parameter

Question

Another way to escape quotes (though probably not preferable), which I've found used in certain places is to use multiple double-quotes. For the purpose of making other people's code legible, I'll explain.

Here's a set of basic rules:

1. When not wrapped in double-quoted groups, spaces separate parameters:
   program param1 param2 param 3 will pass four parameters to program.exe:
        param1, param2, param, and 3.
2. A double-quoted group ignores spaces as value separators when passing parameters to programs:
   program one two "three and more" will pass three parameters to program.exe:
        one, two, and three and more.
Now to explain some of the confusion:
3. Double-quoted groups that appear directly adjacent to text not wrapped with double-quotes join into one parameter:
   hello"to the entire"world acts as one parameter: helloto the entireworld.
Note: The previous rule does NOT imply that two double-quoted groups can appear directly adjacent to one another.
4. Any double-quote directly following a closing quote is treated as (or as part of) plain unwrapped text that is adjacent to the double-quoted group, but only one double-quote:
   "Tim says, ""Hi!""" will act as one parameter: Tim says, "Hi!"

Thus there are three different types of double-quotes: quotes that open, quotes that close, and quotes that act as plain-text.
Here's the breakdown of that last confusing line:

"   open double-quote group
T   inside ""s
i   inside ""s
m   inside ""s
    inside ""s - space doesn't separate
s   inside ""s
a   inside ""s
y   inside ""s
s   inside ""s
,   inside ""s
    inside ""s - space doesn't separate
"   close double-quoted group
"   quote directly follows closer - acts as plain unwrapped text: "
H   outside ""s - gets joined to previous adjacent group
i   outside ""s - ...
!   outside ""s - ...
"   open double-quote group
"   close double-quote group
"   quote directly follows closer - acts as plain unwrapped text: "

Thus, the text effectively joins four groups of characters (one with nothing, however):
Tim says,  is the first, wrapped to escape the spaces
"Hi! is the second, not wrapped (there are no spaces)
 is the third, a double-quote group wrapping nothing
" is the fourth, the unwrapped close quote.

As you can see, the double-quote group wrapping nothing is still necessary since, without it, the following double-quote would open up a double-quoted group instead of acting as plain-text.

From this, it should be recognizable that therefore, inside and outside quotes, three double-quotes act as a plain-text unescaped double-quote:

"Tim said to him, """What's been happening lately?""""

will print Tim said to him, "What's been happening lately?" as expected. Therefore, three quotes can always be reliably used as an escape.
However, in understanding it, you may note that the four quotes at the end can be reduced to a mere two since it technically is adding another unnecessary empty double-quoted group.

Here are a few examples to close it off:

program a b                       REM sends (a) and (b)
program """a"""                   REM sends ("a")
program """a b"""                 REM sends ("a) and (b")
program """"Hello,""" Mike said." REM sends ("Hello," Mike said.)
program ""a""b""c""d""            REM sends (abcd) since the "" groups wrap nothing
program "hello to """quotes""     REM sends (hello to "quotes")
program """"hello world""         REM sends ("hello world")
program """hello" world""         REM sends ("hello world")
program """hello "world""         REM sends ("hello) and (world")
program "hello ""world"""         REM sends (hello "world")
program "hello """world""         REM sends (hello "world")

Final note: I did not read any of this from any tutorial - I came up with all of it by experimenting. Therefore, my explanation may not be true internally. Nonetheless all the examples above evaluate as given, thus validating (but not proving) my theory.

I tested this on Windows 7, 64bit using only *.exe calls with parameter passing (not *.bat, but I would suppose it works the same).

I cannot quickly reproduce the symptoms: if I try myscript '"test"' with a batch file myscript.bat containing just @echo.%1 or even @echo.%~1, I get all quotes: '"test"'

Perhaps you can try the escape character ^ like this: myscript '^"test^"'?

Try this:

myscript """test"""

"" escape to a single " in the parameter.

The 2nd document quoted by Peter Mortensen in his comment on the answer of Codesmith made things much clearer for me. That document was written by windowsinspired.com. The link repeated: A Better Way To Understand Quoting and Escaping of Windows Command Line Arguments.

Some further trial and error leads to the following guideline:

Escape every double quote " with a caret ^. If you want other characters with special meaning to the Windows command shell (e.g., <, >, |, &) to be interpreted as regular characters instead, then escape them with a caret, too.

If you want your program foo to receive the command line text "a\"b c" > d and redirect its output to file out.txt, then start your program as follows from the Windows command shell:

foo ^"a\^"b c^" ^> d > out.txt

If foo interprets \" as a literal double quote and expects unescaped double quotes to delimit arguments that include whitespace, then foo interprets the command as specifying one argument a"b c, one argument >, and one argument d.

If instead foo interprets a doubled double quote "" as a literal double quote, then start your program as

foo ^"a^"^"b c^" ^> d > out.txt

The key insight from the quoted document is that, to the Windows command shell, an unescaped double quote triggers switching between two possible states.

Some further trial and error implies that in the initial state, redirection (to a file or pipe) is recognized and a caret ^ escapes a double quote and the caret is removed from the input. In the other state, redirection is not recognized and a caret does not escape a double quote and isn't removed. Let's refer to these states as 'outside' and 'inside', respectively.

If you want to redirect the output of your command, then the command shell must be in the outside state when it reaches the redirection, so there must be an even number of unescaped (by caret) double quotes preceding the redirection. foo "a\"b " > out.txt won't work -- the command shell passes the entire "a\"b " > out.txt to foo as its combined command line arguments, instead of passing only "a\"b " and redirecting the output to out.txt.

foo "a\^"b " > out.txt won't work, either, because the caret ^ is encountered in the inside state where it is an ordinary character and not an escape character, so "a\^"b " > out.txt gets passed to foo.

The only way that (hopefully) always works is to keep the command shell always in the outside state, because then redirection works.

If you don't need redirection (or other characters with special meaning to the command shell), then you can do without the carets. If foo interprets \" as a literal double quote, then you can call it as

foo "a\"b c"

Then foo receives "a\"b c" as its combined arguments text and can interpret it as a single argument equal to a"b c.

Now -- finally -- to the original question. myscript '"test"' called from the Windows command shell passes '"test"' to myscript. Apparently myscript interprets the single and double quotes as argument delimiters and removes them. You need to figure out what myscript accepts as a literal double quote and then specify that in your command, using ^ to escape any characters that have special meaning to the Windows command shell. Given that myscript is also available on Unix, perhaps \" does the trick. Try

myscript \^"test\^"

or, if you don't need redirection,

myscript \"test\"

I'm calling powershell from cmd, and passing quotes and neither escapes here worked. The grave accent worked to escape double quotes on this Win 10 surface pro.

>powershell.exe "echo la`"" >> test
>type test
la"

Below are outputs I got for other characters to escape a double quote:

la\
la^
la
la~

Using another quote to escape a quote resulted in no quotes. As you can see, the characters themselves got typed, but didn't escape the double quotes.