Double Quotes in batch string redux - windows

Question

I'm trying to understand how the ^ Caret escape works in a Batch CMD. Lets say I type this line in a CMD Window, I would expect it to send the DIR listing to "c:\my text.txt"
CMD.EXE "/C > ^"c:\my text.txt^" DIR C:\*.*"
Instead I get the error:
'txt.txt" DIR *.*"' is not recognized as an internal or external command,
operable program or batch file.
If I do something as simple as this:
ECHO "^"^""
Expected: """"
Actual : "^"""
Even if I try double quoting like this:
ECHO " "" "" "
Expected: " " " "
Actual : " "" "" "
Can someone 'splain how this works and what is a reliable way is to escape double quotes in a command line?
Thanks.
Additional Example:
Why does this work:
cmd.exe "/C sqlcmd.exe -S.\SQLEXPRESS -E -Q"select suser_name()" > "c:\temp\test 1.txt""
but this gives error "The system cannot find the path specified." and does not create the txt file.
cmd.exe "/C "sqlcmd.exe" -S.\SQLEXPRESS -E -Q"select suser_name()" > "c:\temp\test 1.txt""
I know it is not needed in this case, but how would I enclose the command sqlcmd.exe in quotes?
I also tried removing the quotes from the whole line with the same results, i.e.,
cmd.exe /C "sqlcmd.exe" -S.\SQLEXPRESS -E -Q"select suser_name()" > "c:\temp\test 1.txt"
Thanks again.

Answer 1

Quotes are a state machine within cmd.exe. The first quote turns quoting semantics on, the next quote turns it off, the next back on, etc.
It is possible to escape a quote such that it does not turn quote semantics on.
For example, the following will send a quote character to test.txt
echo ^" >test.txt
Without the escape, the string " >test.txt is simply printed to the screen.
Unfortunately, it is not possible to escape a quote that turns off quote semantics.
For example, suppose you want to print the string "hello world" >"test.txt" to the screen. None of the techniques you tried will work because an internal quote cannot be escaped. The ^" form treats the ^ as a literal, and the output will still be redirected to a file. The "" for properly quotes the >, so there is no redirection, but now you have two quotes instead of one.
You have two options.
1) escape all "poison" characters that are not quoted
echo "hello world" ^>"test.txt"
2) hide the quote literal within a delayed expansion variable
I'm assuming this code is in a batch script.
setlocal enableDelayedExpansion
set "quote=""
echo "hello world!quote! >!quote!test.txt"
Note that using this technique can become tricky if dealing with FOR /F ... IN('command') or CMD /C because delayed expansion will probably be off within the new CMD.EXE context.
Here is a way to do your original command
cmd /c dir c:\*.* ^>"c:\my text.txt"
Note that the entire command string after /c does not have to be enclosed within quotes. In this case, it is easier if it is not.
I believe your new command at the end can be written as follows:
cmd.exe /C ""sqlcmd.exe" -S.\SQLEXPRESS -E -Q"select suser_name()" > "c:\temp\test 1.txt""
If used within a parenthesized block, then the right paren will need to be escaped.
(
cmd.exe /C ""sqlcmd.exe" -S.\SQLEXPRESS -E -Q"select suser_name(^)" > "c:\temp\test 1.txt""
)