test25.c

数据结构学习点滴

#include "myhdr.h"
#define MAX 50
/**对于文件FILE *fopen(fp,mode) failure returns NULL,fclose(fp),******/
/****int fread(buffer,sizeof(type),count,fp) returns count***/
/**int fwrite(buffer,sizeof(type),count,fp) returns count***/
/***int fseek(fp,offset,SEEEK_SET) sucessed return 0***/
/**int fprintf(fp,"string\n"),long ftell(fp) return the postion of fp***/
/**void rewind(fp),char *fgets(buf,BUFLEN,fp)**/
/**int fputs(buf,fp),char *gets(type),int puts(string),int fflush(fp)***/
/**int getc(stdin),int getchar(),int putchar(char1)***/
/**int fgetc(fp),int feof(fp),int remove(fp) return 0***/
/***int rename(oldname,newname)return 0****/
/**char *strchr(char *str,int ch) ***/
/****char *strrchr(char *str,int ch***/
/***strcspn(char *buf1,char *buf2) return postion of first char in buf2***/
int 
main()
{
	FILE *fp;
	int data,count,array[MAX];
	long offset;

	for(count=0;count<MAX;count++)
	{
		array[count]=count*10;
	}

	if((fp=fopen("RANDOM.DAT","wb"))==NULL)
	{
		fprintf(stderr,"\nError opening file");
		exit(-1);
	}
	if((fwrite(array,sizeof(int),MAX,fp))!=MAX)
	{
		fprintf(stderr,"\nError writing data to file");
		exit(-1);
	}
	fclose(fp);
	
	if((fp=fopen("RANDOM.DAT","rb"))==NULL)
	{
		fprintf(stderr,"\nError opening file");
		exit(-1);
	}

	while(1)
	{
		printf("\nEnter element to read,0-%d,-1 to exit:",MAX-1);
		scanf("%ld",&offset);
		
		if(offset<0)
			break;
		else if(offset>MAX-1)
			continue;
		if((fseek(fp,(offset*sizeof(int)),SEEK_SET))!=0)
		{
			fprintf(stderr,"\nError using fseek()");
			exit(-1);
		}
		
		fread(&data,sizeof(int),1,fp);
		printf("\nElemnet %ld has value %d",offset,data);
	}
	fclose(fp);
	return 0;
}