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 "); return -1; } printf("open file a.c success "); fputc('a',fp); rewind(fp); ret = fgetc(fp); printf("ret = %c ",ret); ret = fgetc(fp); printf("ret = %d ",ret); printf("1feof=%d,ferror=%d ",feof(fp),ferror(fp)); clearerr(fp); printf("2feof=%d,ferror=%d ",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 "; char readbuf[128] = {0}; char *ret; fp = open("./a.c","w+"); if(fp == NULL){ printf("open file a.c error "); return -1; } printf("open file a.c success "); fput(buf,fp); rewind(fp); fgets(readbuf,128,fp); printf("1readbuf : %s ",readbuf); memset(readbuf,128,0); ret = fgets(readbuf,128,fp); printf("2readbuf = %s,ret=%p ",readbuf,ret); printf("feof=%d,ferror=%d ",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 "); return -1; } src_fp = fopen(argv[1],"r"); if(src_fp == NULL){ printf("open src file %s error ",argv[1]); return -2; } while(1){ read_ret = fgetc(src_fp); if(feof(src_fp)){ printf("read file %s end ",argv[1]); break; } fputc(read_ret,stdout); } fclose(src_fp); return 0; }