Cp - to So loop until we're done wrtot = 0 while(wrtot< len wr = write(tofd buf wrtot len-wrtot if(wr<0 err(1"%s" to wrtot = wr If we

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#include <unistd.h> #include <err.h> /* * cp - copy a file. * Usage: cp oldfile newfile */ /* Copy one file to another. */ static void copy(const char *from, const char *to) { int fromfd; int tofd; char buf[1024]; int len, wr, wrtot; /* * Open the files, and give up if they won't open */ fromfd = open(from, O_RDONLY); if (fromfd<0) { err(1, "%s", from); } tofd = open(to, O_WRONLY|O_CREAT|O_TRUNC); if (tofd<0) { err(1, "%s", to); } /* * As long as we get more than zero bytes, we haven't hit EOF. * Zero means EOF. Less than zero means an error occurred. * We may read less than we asked for, though, in various cases * for various reasons. */ while ((len = read(fromfd, buf, sizeof(buf)))>0) { /* * Likewise, we may actually write less than we attempted
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Unformatted text preview: * to. So loop until we're done. */ wrtot = 0; while (wrtot < len) { wr = write(tofd, buf+wrtot, len-wrtot); if (wr<0) { err(1, "%s", to); } wrtot += wr; } } /* * If we got a read error, print it and exit. */ if (len<0) { err(1, "%s", from); } if (close(fromfd) < 0) { err(1, "%s: close", from); } if (close(tofd) < 0) { err(1, "%s: close", to); } } int main(int argc, char *argv) { /* * Just do it. * * We don't allow the Unix model where you can do * cp file1 file2 file3 destination-directory * * although this would be pretty easy to add. */ if (argc!=3) { errx(1, "Usage: cp OLDFILE NEWFILE"); } copy(argv[1], argv[2]); return 0; }...
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This note was uploaded on 11/10/2009 for the course CS 536 taught by Professor Lums during the Spring '09 term at Indiana.

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Cp - to So loop until we're done wrtot = 0 while(wrtot< len wr = write(tofd buf wrtot len-wrtot if(wr<0 err(1"%s" to wrtot = wr If we

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