Strings and white space

This is a discussion on Strings and white space within the C Programming forums, part of the General Programming Boards category; Is it possible to scan strings with spaces, and then other unlike int variables. For instance, if I wanted to ...

  1. #1
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    Strings and white space

    Is it possible to scan strings with spaces, and then other unlike int variables. For instance, if I wanted to input the name of a tool, then it's price, how would I differentiate between the two in the scan line?

  2. #2
    Guest Sebastiani's Avatar
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    >> Strings and white space

    I don't quite understand what you're asking. Example, please?



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    Here's a sample of code:
    Code:
    void newrecord(FILE *fptr)
    {
    	struct inventory tool = {0, "", 0, 0.0};
    
    	int recordnum;
    
    	printf("Enter new record (1-100): ");
    	scanf("%d", &recordnum);
    
    	fseek(fptr, (recordnum - 1) * sizeof(struct inventory), SEEK_SET);
    
    	fread(&tool, sizeof(struct inventory), 1, fptr);
    
    	if(tool.recordnum != 0){
    		printf("Record #%d already contains information.\n", tool.recordnum);
    	}
    	else{
    		printf("Enter Tool Name, Quantity and Cost: ");
    		scanf("%s%d%lf", &tool.toolname, &tool.quantity,
    			&tool.cost);
    		tool.recordnum = recordnum;
    
    		fseek(fptr, (tool.recordnum - 1) * sizeof(struct inventory), SEEK_SET);
    
    		fwrite(&tool, sizeof(struct inventory), 1, fptr);
    	}/*end else*/
    }
    My problem is that I can't get scanf to differentiate beween the variables for 'toolname' and 'quantity'.

  4. #4
    DESTINY BEN10's Avatar
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    Quote Originally Posted by ginom71 View Post
    Is it possible to scan strings with spaces, and then other unlike int variables. For instance, if I wanted to input the name of a tool, then it's price, how would I differentiate between the two in the scan line?
    If I got your question right, yes it is possible to scan strings with spaces, using fgets. For differentiating the name will be string and price would be int or float. In that case using a structure is advisable.
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  5. #5
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    >> My problem is that I can't get scanf to differentiate beween the variables for 'toolname' and 'quantity'.

    Why? Aren't you entering the values separated by spaces? It should work fine. Oh and one more thing, you should be checking return values (scanf, fseek, fread, etc).



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    I am, but the problem is with input like "Sledge Hammer" and then 7.50 for cost. I need to figure out how to enter strings that have spaces, and then input value for other variables.

  7. #7
    Guest Sebastiani's Avatar
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    >> the problem is with input like "Sledge Hammer" and then 7.50 for cost.

    I see. In that case, you'll either need to input them separately (eg: one variable per line) or else use fgets and split the input "manually".



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  8. #8
    ATH0 quzah's Avatar
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    1 - Read the FAQ.
    2 - Read a line from the file using fgets.
    3 - Split it using sscanf.

    Actually... it looks like you're reading records one whole structure at a time. In which case, you shouldn't need to do any of this. Just fwrite the whole structure, and then later fread it back in.

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  9. #9
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    Here's a quick-and-dirty example using fgets and sscanf:

    Code:
    int main( void )
    {
    	const int
    		size = 1024;
    	char
    		buffer[ size + 1 ];
    	char
    		name[ size + 1 ];
    	int
    		index = 0, 
    		quantity = 0;
    	double	
    		cost = 0;
    	printf( "Enter name, quantity, and cost >" );	
    	if( fgets( buffer, size, stdin ) )
    	{
    		while( buffer[ index ] != 0 && !isdigit( buffer[ index + 1 ] ) )
    			++index;
    		strncpy( name, buffer, index );
    		name[ index ] = 0;
    		if( sscanf( &buffer[ index ], "%d%lf", &quantity, &cost ) == 2 )
    		{
    			printf( "Name: %s\nQuantity: %d\nCost: %lf\n", name, quantity, cost );
    		}
    		else
    		{
    			puts( "Error: invalid input" );
    		}
    	}
    	else
    	{
    		puts( "Error: input error" );
    	}
    	return 0;
    }



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  10. #10
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    Thanks for that. Why do you set name[index] to zero?

  11. #11
    Guest Sebastiani's Avatar
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    >> Why do you set name[index] to zero?

    Just to be sure that it gets null terminated (strncpy doesn't guarantee it).



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    Thanks again for the help. OK, I've changed your code around a little to fit my program. This is the new function prototype to insert a new record. See below:

    Code:
    void newrecord(FILE *fptr)
    {
    	struct inventory tool = {0, "", 0, 0.0};
    
    	int recordnum, i = 0;
    	char temp[30];
    
    	printf("Enter new record (1-100): ");
    	scanf("%d", &recordnum);
    
    	fseek(fptr, (recordnum - 1) * sizeof(struct inventory), SEEK_SET);
    
    	fread(&tool, sizeof(struct inventory), 1, fptr);
    
    	if(tool.recordnum != 0){
    		printf("Record #%d already contains information.\n", tool.recordnum);
    	}
    	else{
    		printf("Enter name, quantity, and cost: ");
    		fgets( temp, 30, stdin );
    		
    		while(temp[i] != 0 && !isdigit(temp[i + 1])){
    			++i;
    		strncpy(tool.toolname, temp, i);
    		tool.toolname[i] = 0;
    		}
    		sscanf( &temp[i], "%d%lf", &tool.quantity, &tool.cost);
    		printf( "Name: %s\nQuantity: %d\nCost: %lf\n", tool.toolname, tool.quantity, tool.cost);
    
    		tool.recordnum = recordnum;
    	}/*end else*/
    }
    Below is a shot of the program when running.

    Press 1 to begin a new file, 2 to use existing data: 1

    Enter your choice
    1 - store a formatted text file of the inventory called
    "storeinv.txt" for printing
    2 - update a record
    3 - add a new record
    4 - delete a record
    5 - end program
    ? 3
    Enter new record (1-100): 3
    Enter name, quantity, and cost: Name:

    Quantity: 0
    Cost: 0.000000

    Enter your choice
    1 - store a formatted text file of the inventory called
    "storeinv.txt" for printing
    2 - update a record
    3 - add a new record
    4 - delete a record
    5 - end program
    ?
    So what happens between the time I enter a new record number and the time I'm supposed to enter data for the record?

  13. #13
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    I have also tried the following:

    Code:
    void eatnewline(void) {
        int x;
        
        do {
            x = getchar();
        } while(x != '\n' && x != EOF);
    }
    Code:
    void newrecord(FILE *fptr)
    {
    	struct inventory tool = {0, "", 0, 0.0};
    
    	int recordnum, tmprcd, i = 0;
    	char temp[30];
    
    	printf("Enter new record (1-100): ");
    	scanf("%d", &recordnum);
    	tmprcd = recordnum;
    
    	fseek(fptr, (recordnum - 1) * sizeof(struct inventory), SEEK_SET);
    
    	fread(&tool, sizeof(struct inventory), 1, fptr);
    
    	if(tool.recordnum != 0){
    		printf("Record #%d already contains information.\n", tool.recordnum);
    	}
    	else{
    		printf("Enter name, quantity, and cost: ");
    		eatnewline();
    		fgets( temp, 30, stdin );
    		
    		while(temp[i] != 0 && !isdigit(temp[i + 1])){
    			++i;
    		strncpy(tool.toolname, temp, i);
    		tool.toolname[i] = 0;
    		}
    		sscanf( &temp[i], "%d%lf", &tool.quantity, &tool.cost);
    		printf( "Name: %s\nQuantity: %d\nCost: %lf\n", tool.toolname, tool.quantity, tool.cost);
    
    		tool.recordnum = tmprcd;
    	}/*end else*/
    }
    which is supposed to take care of the newline character. Only this happens when I run the program. I can't figure it out.

    Press 1 to begin a new file, 2 to use existing data: 1

    Enter your choice
    1 - store a formatted text file of the inventory called
    "storeinv.txt" for printing
    2 - update a record
    3 - add a new record
    4 - delete a record
    5 - end program
    ? 3
    Enter new record (1-100): 3
    Enter name, quantity, and cost: Electric sander 7 57.98
    Name: Electric sander
    Quantity: 7
    Cost: 57.980000

    Enter your choice
    1 - store a formatted text file of the inventory called
    "storeinv.txt" for printing
    2 - update a record
    3 - add a new record
    4 - delete a record
    5 - end program
    ? 2
    Enter record to update(1-100): 3
    Record has no information.

    Enter your choice
    1 - store a formatted text file of the inventory called
    "storeinv.txt" for printing
    2 - update a record
    3 - add a new record
    4 - delete a record
    5 - end program
    ?

  14. #14
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    Sorry, I forgot the code to write the new data into the file. It works now.

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