69 lines
1.8 KiB
C
69 lines
1.8 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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/* This simple program illustrates the use of a umask.
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*
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* First, set your umask to 022 and 'touch file'; the mode will be 0644.
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*
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* Next, run this program and find file1 with the same mode, but execute
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* permissions added, file2 with the explicitly requested 0777 mode, and
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* finally file3 with mode 0711, since we explicitly turned off other
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* permissions.
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*
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* Observe that each time the flags passed to open(2) are identical.
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*/
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#include <sys/types.h>
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#include <sys/stat.h>
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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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void
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myOpen(const char *path) {
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int fd;
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if ((fd = open(path, O_CREAT | O_EXCL | O_WRONLY,
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S_IRUSR | S_IWUSR | S_IXUSR |
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S_IRGRP | S_IWGRP | S_IXGRP |
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S_IROTH | S_IWOTH | S_IXOTH)) == -1) {
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fprintf(stderr, "Unable to create %s: %s\n",
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path, strerror(errno));
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exit(EXIT_FAILURE);
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}
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(void)close(fd);
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}
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int
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main() {
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/* current umask from your shell will apply to 'file1' */
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myOpen("file1");
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umask(0);
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/* turning all bits off means we will allow
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* all the bits specified in open(2) */
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myOpen("file2");
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umask(S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
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/* turning group/other permissions off in the
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* umask means they won't be set in open(2) */
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myOpen("file3");
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return EXIT_SUCCESS;
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}
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