X = SHELL
in [Programming]
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From: USH on 15 May 2010 21:05 Hi all is there any difference between this.. Shell ("R:\provaclick.exe") and this .. X = Shell ("R:\provaclick.exe") ...? tx !
From: Chip Pearson on 16 May 2010 05:45 If you have no need for the return value of Shell (e.g., detecting when the Shell'd program terminates), then the two are the same. Cordially, Chip Pearson Microsoft Most Valuable Professional, Excel, 1998 - 2010 Pearson Software Consulting, LLC www.cpearson.com On Sat, 15 May 2010 18:05:01 -0700, USH <USH(a)discussions.microsoft.com> wrote: >Hi all is there any difference between this.. > >Shell ("R:\provaclick.exe") > >and this .. > >X = Shell ("R:\provaclick.exe") > >..? tx !
From: Jacob Skaria on 16 May 2010 08:39 If assigned to a variable the Shell command runs an executable program and returns a Variant (Double) representing the program's task ID if successful, otherwise it returns zero. The task ID is a unique number that identifies the running program. -- Jacob (MVP - Excel) "USH" wrote: > Hi all is there any difference between this.. > > Shell ("R:\provaclick.exe") > > and this .. > > X = Shell ("R:\provaclick.exe") > > ..? tx !
From: Rick Rothstein on 16 May 2010 10:32 Shell is a function, which means it returns a value. In VB, however, you have the ability to call any function as if it were a subroutine... the function's value will still be calculated (it gets assigned to a memory location consistent in size with the function's declared return value data type), it just that the value won't be returned anywhere (the memory location eventually gets cleared by VB's "garbage collection" routines whether it was assigned anywhere or not). So the quick answer is the two statements are the same. HOWEVER, that is only because you used the required argument to the Shell function and omitted its optional second argument. IF you had specified that optional second argument, your first statement would have failed with an error whereas your second statement would still have worked correctly. "Why is that?", I am sure you are asking. It has to do with how subroutines are called in VB. The proper syntax for calling a subroutine in VB are these... YourSubroutine Argument1, Argument2, etc. Call YourSubroutine(Argument1, Argument2, etc.) Notice that the first calling method's syntax does not use parentheses whereas the second one's syntax does. Whenever you use parentheses around something in VB that is NOT required by syntax, VB treats it as an expression to be evaluated. If the expression inside the parentheses is a constant or variable reference, then it evaluates to itself. Now, let's examine the two possible ways your originally posted first statement could have been written... Without 2nd argument: Shell ("R:\provaclick.exe") or With 2nd argument: Shell ("R:\provaclick.exe", 2) where the 2 in the "with 2nd argument" example is the default value for that argument when omitted (the 2 is assumed in the first example). Okay, as I said, a SINGLE constant (or variable) value inside parentheses evaluates to itself, so ("R:\provaclick.exe") gets evaluated to "R:\provaclick.exe" and that ends up getting passed to the Shell function. However, in the second example, ("R:\provaclick.exe", 2) is not an expression that VB can evaluate... there are two terms with a comma instead of an operator between them... that is meaningless to VB, so it doesn't know what to pass to the Shell function and errors out instead. So, based on this, my advice when would be to only use parentheses where they are required by syntax or for grouping terms in an expression in order to force the order those terms are evaluated in. Your first posted statement does not meet that criteria and, so you don't end up scratching your head in the future when you end up grouping multiple arguments in a subroutine call, I would recommend against using it. -- Rick (MVP - Excel) "USH" <USH(a)discussions.microsoft.com> wrote in message news:85215E33-03A4-4931-B7FC-75C8A5FF94A9(a)microsoft.com... > Hi all is there any difference between this.. > > Shell ("R:\provaclick.exe") > > and this .. > > X = Shell ("R:\provaclick.exe") > > ..? tx !
From: Jacob Skaria on 17 May 2010 00:39
If assigned to a variable the executable program returns a Variant (Double) representing the program's task ID if successful, otherwise it returns zero. The task ID is a unique number that identifies the running program. -- Jacob (MVP - Excel) "USH" wrote: > Hi all is there any difference between this.. > > Shell ("R:\provaclick.exe") > > and this .. > > X = Shell ("R:\provaclick.exe") > > ..? tx ! |