A data in file How is it stored in?

character All with ASCII code Value form storage ， Numerical data Both can be used ASCII storage , you can also use Stored in binary form.

For example:

Test code:

 

VII Determination of the end of file reading:

7.1 wrong use of feof function:

7.2 # how to judge whether the file reading is finished:

7.2.1 text documents:

7.2.2 binary file:

7.3 # use of feof function:

 

//Write code and put example Txt file and put it in example2 Txt
//From example Txt file and put it into example2 Txt file, read one, write one
int main()
{
	FILE* pfread = fopen("example.txt", "r");
	if (pfread == NULL)
	{
		//Open the file example Txt failed
		perror("fopen");
		return 1;
	}
	else
	{
		//Open the file example Txt successful
		FILE* pfwrite = fopen("example2.txt", "w");
		if (pfwrite == NULL)
		{
			//Open the file example2 Txt failed
			perror("fopen");
			//Open example Txt file successfully, open example2 Txt file failed
			fclose(pfread);	
			pfread = NULL;
			return 1;
		}
		else
		{
			//Open the file example2 Txt successful
			//Read write file
			int ch = 0;
			while ((ch=fgetc(pfread)) != EOF)
			{
				//write file
				fputc(ch, pfwrite);
			}
		
			//Suppose the file example The data in txt contains the string abcdef, while. After the fgetc function reads the character a, the pointer shifts back. When the second fgetc function reads the character b, the character b
			//A new file is written, and then the pointer is shifted back by one element. At this time, the character a is not written to the new file, so an error will occur

			//Therefore, for the file operation function fgets, because this function will automatically offset the position of the file pointer variable, generally do not use chain access, which is prone to error.

			//while ((fgetc(pfread)) != EOF)
			//{
			//	//Write file
			//	fputc(fgetc(pfread), pfwrite);
			//}

		}
		//Close file
		fclose(pfwrite);
		pfwrite = NULL;
	}
	//Close file
	fclose(pfread);
	pfread = NULL;
	return 0;
}

Example 2

1. ferror function:

int ferror ( FILE * stream );

If it is a read failure, that is, a read error, an int integer other than 0 is returned; otherwise, an int integer 0

2. feof function:

int feof ( FILE * stream );

If the end of the file is encountered, that is, the end of the file, an int integer other than 0 will be returned; otherwise, an int integer 0

1, Examples of text files:

#include <stdio.h>
#include <stdlib.h>
int main(void)//No reference
{
	int c=0;    // Note: int, not char, requires EOF
	FILE* fp = fopen("test.txt", "r");
	if (!fp)//If the file fails to be opened, NULL pointer will be returned. NULL pointer is essentially 0. 0 means false,! 0, that is, if the logic is negative, it is true
	{
		//fail to open file
		perror("File opening failed");
		return 1;
	}
	//The fgetc function will return EOF
	//For the file operation function fgetc, do not use chain access, which is prone to error
	while ((c = fgetc(fp)) != EOF)  // Standard C I / O read file cycle
	{
		putchar(c);
	}
	//Determine the reason why the reading ended
	if (ferror(fp))
	{
		puts("I/O error when reading");
	}
	if (feof(fp))
	{
		puts("End of file reached succ	essfully");
	}
	//Close file
	fclose(fp);
	fp = NULL;
}

2, Examples of binary files:

#include <stdio.h>
enum { SIZE = 5 };
int main(void) {
	double a[SIZE] = { 1., 2., 3., 4., 5. };
	FILE *fp = fopen("test.bin", "wb"); // Binary mode must be used
	fwrite(a, sizeof *a, SIZE, fp); // Write array of double
	fclose(fp);
	double b[SIZE];
	fp = fopen("test.bin", "rb");
	size_t ret_code = fread(b, sizeof *b, SIZE, fp); // Read the array of double
	if (ret_code == SIZE) {
		puts("Array read successfully, contents: ");
		for (int n = 0; n < SIZE; ++n) printf("%f ", b[n]);
		putchar('\n');
	}
	else { // error handling
		if (feof(fp))
			printf("Error reading test.bin: unexpected end of file\n");
		else if (ferror(fp)) 
		{
			perror("Error reading test.bin");
		}
	}
	//Close file
	fclose(fp);
	fp = NULL;
}

VIII File buffer: