41 lines
849 B
C
41 lines
849 B
C
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#include <inc/lib.h>
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void
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umain(int argc, char **argv)
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{
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int rfd, wfd;
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char buf[512];
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int n, r;
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if ((rfd = open("/newmotd", O_RDONLY)) < 0)
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panic("open /newmotd: %e", rfd);
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if ((wfd = open("/motd", O_RDWR)) < 0)
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panic("open /motd: %e", wfd);
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cprintf("file descriptors %d %d\n", rfd, wfd);
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if (rfd == wfd)
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panic("open /newmotd and /motd give same file descriptor");
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cprintf("OLD MOTD\n===\n");
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while ((n = read(wfd, buf, sizeof buf-1)) > 0)
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sys_cputs(buf, n);
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cprintf("===\n");
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seek(wfd, 0);
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if ((r = ftruncate(wfd, 0)) < 0)
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panic("truncate /motd: %e", r);
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cprintf("NEW MOTD\n===\n");
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while ((n = read(rfd, buf, sizeof buf-1)) > 0) {
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sys_cputs(buf, n);
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if ((r = write(wfd, buf, n)) != n)
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panic("write /motd: %e", r);
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}
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cprintf("===\n");
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if (n < 0)
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panic("read /newmotd: %e", n);
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close(rfd);
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close(wfd);
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}
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