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C++ Discussion Thread
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May 31st, 2009

Emptying char MAX_PATH array?

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This is a very simple problem, but for some reason I can't get it to work. I need to empty a variable ( char fileName[MAX_PATH] =""; ).

It needs to be to where when I use this that it sees if it equals "", this wont work if it equals NULL will it?:

CPP Syntax (Toggle Plain Text)
if (fileName = "")
{
}
if (fileName = "")
{
}

How could I do this? I have tried:

CPP Syntax (Toggle Plain Text)
fileName = "";
fileName = NULL;
fileName[MAX_PATH] = "";
fileName = "";
fileName = NULL;
fileName[MAX_PATH] = "";

Those all return errors, why can't I empty the variable?

Last edited by killdude69; May 31st, 2009 at 2:33 am.

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killdude69

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May 31st, 2009

Re: Emptying char MAX_PATH array?

Use memset...

memset(fileName, 0, MAX_PATH);

Rewrites the elements to 0.

Yiuca

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May 31st, 2009

Re: Emptying char MAX_PATH array?

Keep it simple:

C++ Syntax (Toggle Plain Text)
fileName[0] = '\0';
// or even
*fileName = 0;
// to test:
if (*fileName) { // non-empty
fileName[0] = '\0';
// or even
*fileName = 0;
// to test:
if (*fileName) { // non-empty

ArkM

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May 31st, 2009

Re: Emptying char MAX_PATH array?

How would I test if it IS empty.
Because I am currently using: if (fileName == "")

And I am using this for over 6 if statments.

killdude69

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May 31st, 2009

Re: Emptying char MAX_PATH array?

Click to Expand / Collapse Quote originally posted by killdude69 ...

How would I test if it IS empty.
Because I am currently using: if (fileName == "")

And I am using this for over 6 if statments.

Didn't you familiar with logical not operator?

C++ Syntax (Toggle Plain Text)
if (!*fileName)
// or
if (fileName[0] == '\0')
// or
if (strlen(fileName) == 0)
if (!*fileName)
// or
if (fileName[0] == '\0')
// or
if (strlen(fileName) == 0)

By the way, fileName == "" is equal to false in all cases. Why? Think about pointers comparison

ArkM

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May 31st, 2009

Re: Emptying char MAX_PATH array?

I know how to use logical operators, I just wasn't sure if !* was even valid.

the strlen() aproach seems best to me ArkM, I will try it.

killdude69

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May 31st, 2009

Re: Emptying char MAX_PATH array?

Sorry for the DP, but I just want to let you know, ArkM, that that worked perfectly. Thanks to you to Yiucia, I used your memset approach. Rep for you all. Problem solved.

And just so you know, I am a decent programmer, don't be fooled by this simple question

killdude69

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