60 lines
1.3 KiB
C
60 lines
1.3 KiB
C
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/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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/*
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* If you create a new file, write, say,
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* 10 bytes of data, and then seek to the
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* end of the file, where do you end up? Why?
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*/
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#define WFILE "/tmp/rw"
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#define DLEN 10
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int
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main() {
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int fd, n;
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char data[DLEN];
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bzero(data, DLEN);
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if ((fd = open(WFILE, O_RDWR | O_CREAT | O_EXCL, 0700)) == -1) {
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fprintf(stderr, "Unable to open '%s': %s\n",
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WFILE, strerror(errno));
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exit(EXIT_FAILURE);
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}
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if (write(fd, data, DLEN) != DLEN) {
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fprintf(stderr, "Unable to write: %s\n",
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strerror(errno));
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exit(EXIT_FAILURE);
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}
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if ((n = lseek(fd, 0, SEEK_END)) == 0) {
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fprintf(stderr, "Unable to seek: %s\n",
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strerror(errno));
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exit(EXIT_FAILURE);
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}
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printf("Seeked to offset %d\n", n);
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(void)close(fd);
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return EXIT_SUCCESS;
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}
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