系統io讀寫，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; }

標準io讀寫操作.........................

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是真正讀取到的數據塊個數 n<=5 ???????? // 100 --> 5 ???????? // 98? --> 4 ???????? // 80? --> 4 ???????? // 21? --> 1 ???????? // 19? --> 0 ???????? // 1? --> 0

??if(nread == 5) // 正常讀取 ?

?{ ???char *p = buf; ??

?while(nread > 0) ???{

????nwrite = fwrite(p, 20, nread, fp2); // nwrite <= n ???

?nread -= nwrite; ?

???p += nwrite*20; ???}

??}

??else if(nread >= 0) // 到達文件尾部 ?

?{ ???long end = ftell(fp1); ?

??fwrite(buf, end-begin, 1, fp2); ?

??break;

??}

??else // 讀取出錯了 ?

?{ ???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); // 從fp1讀取一行（最多19字節）放到buf中

??if(tmp == NULL) ??{

???// 1. 遇到了錯誤 ??

?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. 遇到錯誤 ?

??if(ferror(fp1)) ???

{ ????perror("fgetc() failed");

????break; ???}

???// 2. 遇到文件尾 ??

?if(feof(fp1)) ???{

????printf("copy completed.\n"); ??

??break; ???} ?

?}

??fputc(ch, fp2);

?}

?

轉載于:https://www.cnblogs.com/defen/p/5242822.html

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