Endfile loops with data sets

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The endfile loop explicitly detects the end the input at the end of the file.

The EOF (End Of File) is the end of that input stream, such as a keyboard for the standard input, an input file (for the standard input), an actual file, or some other stream. The endfile loop is most similar to the trailer loop. (Likewise, the header loop is most similar to the counter loop)

There can only be one endfile loop for each file.

How is and endfile loop best done when each line of data has more than one number? Let us look at some examples with more than one data number per line.

See the following for more information.

Many programming languages either raise a run-time error when trying to read past the end of file, or provide no run-time error but may or may not work as desired. C is such a language.

Here is the C code.

#include <stdio.h>

int main() {
	int pos1;
	int len1;
	int value1;
	int value2;
	int value3;
	// endfile loop
	printf("Enter data sets of three numbers until end of input.\n");
	printf("\n");
	scanf("%d %d %d",&value1,&value2,&value3);
	pos1 = 0;
	while (! feof(stdin)) {
		pos1 += 1;
		printf("%d. Data set %d is: %d %d %d\n",pos1,pos1,value1,value2,value3);
		scanf("%d %d %d",&value1,&value2,&value3);
		}
	len1 = pos1;
	printf("\n");
	printf("End of file found.\n");
	printf("%d data sets found.\n",len1);
	return 0;
	}

4. Examples of input and output

Here are some examples of input and output for the above program code.

Here is an example input.

11 22 33
44 55 66
77 88 99

For the above example input, here is the expected output.

Enter data sets of three numbers until end of input.

1. Data set 1 is: 11 22 33
2. Data set 2 is: 44 55 66

End of file found.
2 data sets found.

Here is an example input.

22 33 44
55 66 77

For the above example input, here is the expected output.

Enter data sets of three numbers until end of input.

1. Data set 1 is: 22 33 44

End of file found.
1 data sets found.

Here is an example input. For the above example input, here is the expected output.

Enter data sets of three numbers until end of input.


End of file found.
0 data sets found.

When there is no data to be read, the programming language C will just read empty values, zeros for numbers, without an error.

Some programming languages will raise an error if an attempt is made to read beyond the end of the data.

Here is a way to handle this. Note only one value is input before determining whether the trailer value has been read. Here is the C code.

#include <stdio.h>

int main() {
	int pos1;
	int len1;
	int value1;
	int value2;
	int value3;
	// endfile loop
	printf("Enter data sets of three numbers until end of input.\n");
	printf("\n");
	scanf("%d",&value1);
	pos1 = 0;
	while (! feof(stdin)) {
		scanf("%d %d",&value2,&value3);
		pos1 += 1;
		printf("%d. Data set %d is: %d %d %d\n",pos1,pos1,value1,value2,value3);
		scanf("%d",&value1);
		}
	len1 = pos1;
	printf("\n");
	printf("End of file found.\n");
	printf("%d data sets found.\n",len1);
	return 0;
	}

Here are some examples of input and output for the above program code.

Here is an example input.

11 22 33
44 55 66
77 88 99

For the above example input, here is the expected output.

Enter data sets of three numbers until end of input.

1. Data set 1 is: 11 22 33
2. Data set 2 is: 44 55 66
3. Data set 3 is: 77 88 99

End of file found.
3 data sets found.

Here is an example input.

22 33 44
55 66 77

For the above example input, here is the expected output.

Enter data sets of three numbers until end of input.

1. Data set 1 is: 22 33 44
2. Data set 2 is: 55 66 77

End of file found.
2 data sets found.

Here is an example input. For the above example input, here is the expected output.

Enter data sets of three numbers until end of input.


End of file found.
0 data sets found.

Note: In the above, note that when there is no input or input file, no input file is displayed.

As an exercise, try changing the above examples to use parallel arrays of element variables and then an array of records with named field variables.

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