标准I/O函数之fopen, fread, fwrite,fgetc,fputc

#include <stdio.h>#define SIZE 1024/*I/O缓冲：有了缓冲机制以后，多个读写操作可以合并为一次系统调用，减少了系统调用的次数，将大大提高程序的运行效率。标准I/O中，一个打开的文件称为流(stream)，流可以用于读(输入流)、写(输出流)或读写(输入输出流)。每个进程在启动后就会打开三个流，分别对应：stdin(标准输入流)、stdout(标准输出流)以及stderr(标准错误输出流)*//*fopen:#include <stdio.h>FILE *fopen(const char *path, const char *mode);"r"或"rb"：以只读方式打开。"w"或"wb"：以只写方式打开，并把文件长度截短为零。"a"或"ab"：以写方式打开，新内容追加在文件尾。"r+"或"rb+"或"r+b"：以更新方式打开(读和写)。"w+"或"wb+"或"w+b"：以更新方式打开，并把文件长度截短为零。"a+"或"ab+"或"a+b"：以更新方式打开，新内容追加在文件尾。注：字母b表示文件是一个二进制文件而不是文本文件*/int main1(){ //标准I/O函数并不直接操作文件描述符，而是使用文件指针//FILE *fp = fopen("fopen.c","w+");//FILE *fp = fopen("ffopen.c","a+");FILE *fp = fopen("fffopen.c","r+");if(fp == NULL){perror("fopen ");return -1;}else{printf("success\n");}return 0;}/*fread:#include <stdio.h>size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream);    数据从文件流stream读到ptr指向的数据缓冲区里。size参数指定每个数据记录的长度，nmemb给出要传输的记录的个数。函数的返回值是成功读到数据缓冲区里的记录的个数(不是字节数)。*/int main2(){FILE *fp = fopen("sqstack.c","ab+");if(fp == NULL){perror("fopen ");return -1;}char buf[SIZE] = {0};int ret;while(ret = fread (buf,sizeof(char),SIZE-1,fp)){buf[ret*sizeof(char)] = '\0';printf("%s\n",buf);}//feof()只用于测试流文件的结束，当到达结尾时，返回非0if(ret == 0 && !feof(fp)){perror("fread ");return -1;}printf("read over\n");fclose(fp);return 0;}/*fwrite()从指定的数据缓冲区里取出数据记录，并把它们写到输出流中#include <stdio.h>size_t fwrite(const void *ptr, size_t size, size_t nmemb,FILE *stream);它的返回值是成功写入的记录个数。*/int main3(){FILE *fp = fopen("sqstack.c","ab+");if(fp == NULL){perror("fopen ");return -1;}FILE *fp1 = fopen("stack.c","ab+");if(fp == NULL){perror("fopen ");return -1;}char buf[SIZE] = {0};int ret;while(ret = fread (buf,sizeof(char),SIZE-1,fp)){fwrite (buf,sizeof(char),SIZE-1,fp1);}//feof()只用于测试流文件的结束，当到达结尾时，返回非0if(ret == 0 && !feof(fp)){perror("fread ");return -1;}printf("read over\n");fclose(fp);fclose(fp1);return 0;}/*fgetc() :  从文件流里取出下一个字节并把它作为一个字符返回。当它到达文件结尾或出现错误时，返回EOF#include <stdio.h>int fgetc(FILE *stream);int getc(FILE *stream);int getchar(void);fputc():fputc()把一个字符写到一个输出文件流中，它返回写入的值，如果失败，则返回EOF。#include <stdio.h>int fputc(int c, FILE *stream);int putc(int c, FILE *stream);int putchar(int c);*/int main(){FILE *fp = fopen("sqstack.c","ab+");if(fp == NULL){perror("fopen ");return -1;}FILE *fp1 = fopen("qsstack.c","ab+");if(fp == NULL){perror("fopen ");return -1;}/*char buf[SIZE] = {0};while(1){int c = fgetc(fp);if(c == EOF)break;fputc(c,fp1);}*/int c = fgetc(fp);while(c != EOF){fputc(c,fp1);c = fgetc(fp);}if(feof(fp)){printf("read over\n");}else{printf(" something went wrong\n");}fclose(fp);fclose(fp1);return 0;}