When using truncate(), EBADF is sometimes improperly returned. susv3
doesn't list this as a possible errno value for this function. In
particular, ENOENT should be returned when when path doesn't exist and
EACCES when write permission is denied.
truncate.c:
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
int main(int argc, char **argv) {
off_t size;
char *endptr = argv[2];
if (argc != 3) {
fprintf(stderr, "usage: truncate path size\n");
exit(1);
}
errno = 0;
size = strtoull(argv[2], &endptr, 10);
if (!endptr || endptr == argv[2] || *endptr || size < 0 ||
(size == 0 && errno)) {
fprintf(stderr, "truncate: invalid size\n");
exit(1);
}
printf("truncating %s to %lld bytes\n", argv[1], size);
if (truncate(argv[1], size)) {
int saveerr = errno;
perror("truncate");
fprintf(stderr, "errno was %d\n", saveerr);
exit(1);
}
exit(0);
}
======================================================================
$ rm foo
$ ./truncate foo 0
truncating foo to 0 bytes
truncate: Bad file descriptor
errno was 9
$ touch foo
$ chmod u-w foo
$ ls -l foo
-r--r--r-- 1 sthoenna None 0 Dec 1 00:06 foo
$ ./truncate foo 0
truncating foo to 0 bytes
truncate: Bad file descriptor
errno was 9
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