C标准库提供的用于读写文件的函数非常多，大多数函数都在stdio.h中声明.
fread/fwrite，fgets/fputs，fgetchar/fputchar，fprintf/fscanf.............
这些函数原型声明都在stdio.h中,如下：
size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);
size_t fwrite(const void *ptr, size_t size, size_t nmemb,FILE *stream);
int fgetc(FILE *stream);
char *fgets(char *s, int size, FILE *stream);
int getc(FILE *stream);
int getchar(void);
int ungetc(int c, FILE *stream);
无论是写入文件还是从文件流流中读取，都要先打开文件，完成后还要将打开的文件关闭。
为了防止指针变成野指针，还应将文件指针指向NULL。
FILE *fopen(const char *pathname, const char *mode);
FILE *fdopen(int fd, const char *mode);
FILE *freopen(const char *pathname, const char *mode, FILE *stream);
fopen函数的安全版本是fopen_s(FILE *stream,char *filename,char *mode),使用之前要将宏
fileutil.h
#ifndef __FILEUTIL_H
#define __FILEUTIL_H
#include <stdio.h>
FILE *open_file(const char *file,const char *mode);
void read0(const char *file);
void read1(const char *file);
void read2(const char *file);
void write1(const char *file);
#endif
fileutil.c
/*
* =====================================================================================
* Filename: fileutil.c
* Description:
* Version: 1.0
* Created: 2017年04月13日 09时38分23秒
* Revision: none
* Compiler: gcc
* Author: YOUR NAME (),
* Organization:
* =====================================================================================
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "fileutil.h"
FILE *
open_file(const char *file,const char *mode)
{
FILE *fp;
if(!(fp = fopen(file,mode))){
perror("open file error");
exit(-1);
}
return fp;
}
void read0(const char *file)
{
FILE *fp = open_file(file,"r");
char buf[BUFSIZ] = {0};
unsigned long t = 0;
//int tmp = fread(buf,1,20,fp);
//printf("read %d bytes\n",tmp);
//printf("read buf from %s is %s\n",file,buf);
while((t = fread(buf,1,192,fp)) != 0){
printf("%s\n",buf);
bzero(&buf,sizeof(buf));
}
if(fclose(fp) != 0) perror("close file error");
}
void read1(const char *file)
{
FILE *fp = open_file(file,"r");
char *buf;
size_t n = 0;
while((n = getline(&buf,&n,fp)) != (size_t)-1){
printf("%s",buf);
bzero(buf,sizeof(buf));
}
//if(buf) free(buf);
if(fclose(fp) != 0) perror("close file error");
}
void read2(const char *file)
{
FILE *fp = open_file(file,"r");
char buf[BUFSIZ] = "";
while(fgets(buf,BUFSIZ,fp)){
printf("%s",buf);
bzero(buf,BUFSIZ);
}
if(fclose(fp) != 0) perror("close file error");
}
/* 尚未实现 */
void write1(const char *file)
{
FILE *fp = open_file(file,"a+t");
if(fclose(fp) != 0) perror("close file error");