How do I reset a char variable back to its original state?

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May 27th, 2011, 07:18 PM

Dakaa

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how do i set char? (stucked here for 2 hours)

Let me rephrase my question.

Example code:

Code:

	char fileName[128] = "essay";
	char fileNumber[128];
	char *fileFormat = ".doc";

	itoa(0, fileNumber, 10);
	strcat(fileName, fileNumber);
	strcat(fileName, fileFormat);
	printf("%s\n", fileName);

	itoa(1, fileNumber, 10);
	strcat(fileName, fileNumber);
	strcat(fileName, fileFormat);
	printf("%s\n", fileName);

	itoa(2, fileNumber, 10);
	strcat(fileName, fileNumber);
	strcat(fileName, fileFormat);
	printf("%s\n", fileName);

Result:

Code:

essay0.doc
essay0.doc1.dat
essay0.doc1.dat2.dat

What I want is:

Code:

essay0.doc
essay1.doc
essay2.doc

Hope you can see what I mean, I need a method that can set fileName[128] back to JUST the word essay. I want to get rid of the old stuff(number and file format string) at behind.

May 27th, 2011, 07:50 PM

requinix

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Unless you actually want to modify helloString every time, you can just print the two strings separately.

As far as output is concerned, your desired code is equivalent to

Code:

char helloString[128] = "Hello";

for (i = 0; i < 3; i++) {
	printf("%s%d\n", helloString, i);
}

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May 27th, 2011, 08:03 PM

Dakaa

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Quote:

Originally Posted by requinix

Unless you actually want to modify helloString every time, you can just print the two strings separately.

As far as output is concerned, your desired code is equivalent to

Code:

char helloString[128] = "Hello";

for (i = 0; i < 3; i++) {
	printf("%s%d\n", helloString, i);
}

hey sir, is there any method i can store this "("%s%d\n", helloString, i)" into a char? i need it as a file name, cuz i have 3 files, each named XXXfile1, XXXfile2, XXXfile3.

May 27th, 2011, 08:15 PM

LittleGrin

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Look up sprintf(). Use it to create a formatted string, and then printf() that string.

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May 27th, 2011, 10:10 PM

Dakaa

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woot, strncpy() works.

May 28th, 2011, 02:14 AM

clifford

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Quote:

Originally Posted by Dakaa

woot, strncpy() works.

Yes of course it does, but that does not make it a good idea!

Code:

	char fileName[32] ;
        int i ;

        for( i = 0; i < 3; i++ )
        {
            sprintf( "essay%d.doc", i ) ;
            printf( "%s\n", fileName ) ;
        }

For all sorts of cautions regarding string handling in C, especially strcat() read

Code:

this

.

If you wanted to go with your original method then you could have also done this:

Code:

	char fileName[128] = "essay";
	char fileNumber[128];
	char *fileFormat = ".doc";
        char* truncate = &fileName[strlen(fileName)] ;

        // reset fileName
        *truncate = 0 ;

This will overwrite the first digit of the essay number with a string terminator. It is somewhat more efficient that a strcpy(), but more importantly truly sets the string to its original value, whereas with strcpy() you are copying new data that just happens to be the same as the original; more error prone perhaps, and certainly more of a maintenance issue.

How do I reset a char variable back to its original state?

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