file_encrypt.cpp

本程序介绍了如何用C语言快速读写磁盘文件。

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

void file_encrypt()
{
	FILE *fp;
	int i,j;
	char str[1024];

	fp = fopen( "F:\\Backup\\C_Sample\\File_operating\\File_testing.txt", "r+" );
	if(fp == NULL)
	{
		printf("cannot open the file\n");
		exit(0);
	}

	i = 0;
	while(1)
	{
		str[i] = fgetc(fp);
		if( feof(fp) )     //fp overflow,reach the end of file.
			break;

		str[i++] += 1;
	//	str[i++] -= 1;
	}

	fseek(fp,0L,SEEK_SET);
	for( j = 0; j < i; j++ )
		fputc(str[j],fp);

	fclose(fp);

	printf("please check the File_testing.txt file\n");
	return;
}