1. 当返回错误时，怎样判读是已经到达文件结尾，还是读错呢？
a. int feof(FILE *stream);
功能：判断是否已经到文件结束
参数：文件流
返回值：到文件结束，返回为非0，没有则返回0
b.int ferror(FILE *stream);
功能：判断是否读写错误
参数：文件流
返回值：是读写错误，返回为非0，不是则返回0
c.void clearerr(FILE *stream);
功能：清除流错误
参数：文件流
2. 通过检查fgetc的返回值，判断是文件尾还是出错
#include "stdio.h"
int main(int argc, char *argv[]){
FILE *fp;
int ret;
fp = open("./a.c","w+");
if(fp == NULL){
printf("open file a.c error\n");
return -1;
}
printf("open file a.c success\n");
fputc('a',fp);
rewind(fp);
ret = fgetc(fp);
printf("ret = %c\n",ret);
ret = fgetc(fp);
printf("ret = %d\n",ret);
printf("1feof=%d,ferror=%d\n",feof(fp),ferror(fp));
clearerr(fp);
printf("2feof=%d,ferror=%d\n",feof(fp),ferror(fp));
fclose(fp);
return 0;
}
3. 通过检查fgets的返回值，判断是文件尾还是出错
#include "stdio.h"
int main(int argc, char *argv[]){
FILE *fp;
char buf[] = "hello linux\n";
char readbuf[128] = {0};
char *ret;
fp = open("./a.c","w+");
if(fp == NULL){
printf("open file a.c error\n");
return -1;
}
printf("open file a.c success\n");
fput(buf,fp);
rewind(fp);
fgets(readbuf,128,fp);
printf("1readbuf : %s\n",readbuf);
memset(readbuf,128,0);
ret = fgets(readbuf,128,fp);
printf("2readbuf = %s,ret=%p\n",readbuf,ret);
printf("feof=%d,ferror=%d\n",feof(fp),ferror(fp));
fclose(fp);
return 0;
}
4. 例 cat 命令的实现
#include "stdio.h"
#include "unistd.h"
#include "fcntl.h"
#include "string.h"
int main(int argc, char *argv[]){
FILE *src_fp;
int read_ret;
if(argc < 2){
printf("please input src file \n");
return -1;
}
src_fp = fopen(argv[1],"r");
if(src_fp == NULL){
printf("open src file %s error \n",argv[1]);
return -2;
}
while(1){
read_ret = fgetc(src_fp);
if(feof(src_fp)){
printf("read file %s end \n",argv[1]);
break;
}
fputc(read_ret,stdout);
}
fclose(src_fp);
return 0;
}