系统io读写，copy
int main(int argc, char **argv)
{ if(argc != 3)
{ printf("Usage: %s <src> <dst>\n", argv[0]);
exit(0);
}
int fd1, fd2; fd1 = open(argv[1], O_RDONLY);
fd2 = open(argv[2], O_CREAT | O_TRUNC | O_WRONLY);
if(fd1 == -1 || fd2 == -1) { perror("open() failed"); exit(0); }
char buf[100];
int nread;
while(1)
{ bzero(buf, 100); nread = read(fd1, buf, 100);
if(nread == 0) // hits the end of file
{ break;
} if(nread == -1)
{ perror("read() failed");
exit(0);
}
write(fd2, buf, nread); }
close(fd1); close(fd2);
return 0; }
标准io读写操作.........................
fopen-----------------------------------------------------------------fclose范例：
int main(int argc, char **argv) {
if(argc != 3) {
printf("Usage: %s <src> <dst>\n", argv[0]);
exit(0);
}
FILE *fp1 = fopen(argv[1], "r");
if(fp1 == NULL) {
fprintf(stderr, "fopen(%s) failed: %s\n", argv[1], strerror(errno));
exit(0);
}
FILE *fp2 = fopen(argv[2], "w"); if(fp2 == NULL) {
fprintf(stderr, "fopen(%s) failed: %s\n", argv[2], strerror(errno));
exit(0);
}
char *buf = calloc(5, 20);
int nread, nwrite;
while(1) { long begin = ftell(fp1);
nread = fread(buf, 20, 5, fp1); // n是真正读取到的数据块个数 n<=5 // 100 --> 5 // 98 --> 4 // 80 --> 4 // 21 --> 1 // 19 --> 0 // 1 --> 0
if(nread == 5) // 正常读取
{ char *p = buf;
while(nread > 0) {
nwrite = fwrite(p, 20, nread, fp2); // nwrite <= n
nread -= nwrite;
p += nwrite*20; }
}
else if(nread >= 0) // 到达文件尾部
{ long end = ftell(fp1);
fwrite(buf, end-begin, 1, fp2);
break;
}
else // 读取出错了
{ perror("fread() failed");
fclose(fp1);
fclose(fp2);
exit(0);
} }
fclose(fp1);
fclose(fp2);
return 0; }
fgets--------------------------------------------------------------------fputs范例：
while(1) {
char *tmp = fgets(buf, 20, fp1); // 从fp1读取一行（最多19字节）放到buf中
if(tmp == NULL) {
// 1. 遇到了错误
if(ferror(fp1)) {
perror("fgets() failed");
break;
}
// 2. 遇到了文件尾
if(feof(fp1))
{ printf("copy completed.\n");
break;
}
}
fputs(buf, fp2);
}
fgetc----------------------------------------------------------------fputc
while(1) { ch = fgetc(fp1);
if(ch == EOF)
{ // 1. 遇到错误
if(ferror(fp1))
{ perror("fgetc() failed");
break; }
// 2. 遇到文件尾
if(feof(fp1)) {
printf("copy completed.\n");
break; }
}
fputc(ch, fp2);
}
