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POHow does the Windows Command Interpreter (CMD.EXE) parse scripts?
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copied!<p>I ran into <a href="http://www.ss64.com" rel="noreferrer">ss64.com</a> which provides good help regarding how to write batch scripts that the Windows Command Interpreter will run.</p> <p>However, I have been unable to find a good explanation of the <strong>grammar</strong> of batch scripts, how things expand or do not expand, and how to escape things.</p> <p>Here are sample questions that I have not been able to solve:</p> <ul> <li>How is the quote system managed? I made a <a href="http://tinyperl.sourceforge.net/" rel="noreferrer">TinyPerl</a> script<br> ( <code>foreach $i (@ARGV) { print '*' . $i ; }</code> ), compiled it and called it this way : <ul> <li><code>my_script.exe "a ""b"" c"</code> → output is <code>*a "b*c</code></li> <li><code>my_script.exe """a b c"""</code> → output it <code>*"a*b*c"</code></li> </ul></li> <li>How does the internal <code>echo</code> command work? What is expanded inside that command?</li> <li>Why do I have to use <code>for [...] %%I</code> in file scripts, but <code>for [...] %I</code> in interactive sessions?</li> <li>What are the escape characters, and in what context? How to escape a percent sign? For example, how can I echo <code>%PROCESSOR_ARCHITECTURE%</code> literally? I found that <code>echo.exe %""PROCESSOR_ARCHITECTURE%</code> works, is there a better solution?</li> <li>How do pairs of <code>%</code> match? Example: <ul> <li><code>set b=a</code> , <code>echo %a %b% c%</code> → <code>%a a c%</code></li> <li><code>set a =b</code>, <code>echo %a %b% c%</code> → <code>bb c%</code></li> </ul></li> <li>How do I ensure a variable passes to a command as a single argument if ever this variable contains double quotes?</li> <li>How are variables stored when using the <code>set</code> command? For example, if I do <code>set a=a" b</code> and then <code>echo.%a%</code> I obtain <code>a" b</code>. If I however use <code>echo.exe</code> from the UnxUtils, I get <code>a b</code>. How comes <code>%a%</code> expands in a different way?</li> </ul> <p>Thank you for your lights.</p>

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