71 lines
1.2 KiB
C
71 lines
1.2 KiB
C
#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#define BUFSIZE 1024
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/**
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* 可以用 time 命令找到 BUFSIZE 最佳值
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*
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* time ./mycpy /etc/services /tmp/out
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*/
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int main(int argc, char **argv)
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{
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int sfd, dfd;
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char buf[BUFSIZE];
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int len, ret, pos;
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if (argc < 3)
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{
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fprintf(stderr, "Usage: %s <src> <dst>\n", argv[0]);
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exit(1);
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}
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sfd = open(argv[1], O_RDONLY);
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if (sfd < 0)
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{
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perror("open");
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exit(1);
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}
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dfd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0600);
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if (dfd < 0)
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{
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// !!!
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close(sfd);
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perror("open");
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exit(1);
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}
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while (1)
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{
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len = read(sfd, buf, BUFSIZE);
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if (len < 0)
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{
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perror("read");
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break;
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}
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if (len == 0)
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break;
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pos = 0;
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while (len > 0)
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{
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/* 可能没写完被别的中断打断 */
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ret = write(dfd, buf + pos, len);
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if (ret < 0)
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{
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perror("write");
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exit(1);
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}
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pos += ret;
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len -= ret;
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}
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}
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close(dfd);
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close(sfd);
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exit(0);
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} |