Date: Wed, 12 May 2010 17:30:48 -0400 From: Garrett Cooper <yanefbsd@gmail.com> To: hackers@freebsd.org Subject: argv offset -- doesn't make sense... Message-ID: <A28FCE87-10DE-46BB-B22F-E7DF9FD32BCD@gmail.com>
next in thread | raw e-mail | index | archive | help
Hi Hackers,
Ignoring the compiler warning (yes, I know...), why is the =
offset for the argv[0] (program name) in the following program off by =
one? It doesn't make sense why the fstat would work, but the printf =
would fail (and in fact segfault if I remove the 1 < argc guard =
statement and adjusted the offset by removing the +1).
Thanks,
-Garrett
PS I know I'm missing all of the real error checks because I just wanted =
a quick and dirty test app.
# gcc -Wall -O0 -g -o test_fstat test_fstat.c
test_fstat.c: In function 'main':
test_fstat.c:20: warning: format '%lu' expects type 'long unsigned int', =
but argument 3 has type 'off_t'
# ./test_fstat ./test_fstat
argc - 2, argv[0] - ./test_fstat
(null) - 7118
# ./test_fstat ./test_fstat
argc - 2, argv[0] - ./test_fstat
./test_fstat - -790036480
# cat test_fstat.c
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
int
main(int argc, char **argv)
{
if (1 < argc) {
printf("argc - %d, argv[0] - %s\n", argc, *argv);
int fd =3D open(*(argv+1), O_RDONLY);
struct stat *sb;
fstat(fd, sb);
printf("%s - %ld\n", *(argv+1), (long int) sb->st_size);
}
return 0;
}=
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?A28FCE87-10DE-46BB-B22F-E7DF9FD32BCD>