During lunch I grabbed your code and it compiled cleanly. accept() didn't work (on Linux) because intlen wasn't initalized to sizeof(struct inaddr_in).
The way you have keepsake temporarily hold onto the head of the list and iterate using descr_list is odd. So I changed descr_list to be descr_head. It always is the head of the list (Then no need wasting struct space on a list pointer in each and every descr). Then iterate with:
Removed some dead code and it worked.
I think somehow you're getting descr_list to be NULL and trying to reference descr_list->next. Not sure, might look later at the original code but it was easier this way for me.
---------- Post updated at 03:50 PM ---------- Previous update was at 01:35 PM ----------
I looked again at fixing your implimentation and couldn't. I can't wrap my head around where descr_list may be at any given moment since it's a global and changed in a function (initalize_descr) called from main().... here's snipplets of my changes
Last edited by neutronscott; 05-03-2012 at 05:15 PM..
Reason: better loop
Requirements:
A server program should read a file and send the message to the client . if the file is not there, then switch to the receive part of the same program and receive any messages from the socket. If no messages to receive then switch to send part of the program to... (2 Replies)
I ran degugger in C++ and the followings are the message I got:
Program received signal SIGABRT, Aborted.
0x002a57a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
(gdb) info s
#0 0x002a57a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1 0x002e97f5 in raise () from /lib/tls/libc.so.6... (1 Reply)
Dear all,
I used debugger from C++ and these are the message I got:
Program received signal SIGSEGV, Segmentation fault.
0x00323fc0 in free () from /lib/tls/libc.so.6
(gdb) info s
#0 0x00323fc0 in free () from /lib/tls/libc.so.6
#1 0x00794fa1 in operator delete () from... (5 Replies)
Hi,
I would like to write a program to receive the GPS data and then send the data via network to other program.
All of the program is not write yet(include host and sender)
All of the server OS is unix or linux
Could you mind to give me some idea to do this?
Thanks so much!
Ken
... (2 Replies)
Hello,
One of our customer is getting segmentation fault when he runs his shell script which invokes our executable on AIX 6.1.
On AIX 5.3, there were no issues.
Here is the truss output.
811242: __loadx(0x0A040000, 0xF0D3A26C, 0x00000000, 0x00000009, 0x00000000) = 0xF026E884... (0 Replies)
Hi to all,
i am trying to make mksysb backup of a NIM client machine from NIM master and while i am reading that the backup is done successfully i get an error message below and it doesnt exit the smit screen. also the status of the command appears to be running.
is there anybody who knows why... (3 Replies)
I am making a command line program in C using XCode. When running the program, it initially does what it is supposed to do (asks me for a file path). However, when I type in a valid and existing file path, it gives me the following error:
Program received signal: “EXC_BAD_ACCESS”.... (6 Replies)
in a single main() function,so need signal handling. Use Posix Message Queue IPC mechanism , can ignore the priority and other linked list message,to implement the scenario:
client:Knock Knock
server:who's there
client: Eric
Server:Eric,Welcome.
client:exit
all process terminated
... (1 Reply)
hi all
I am getting following error while taking backup
using the command
ufsdump 0ubf 512 /dev/rmt/0cbn /database/backup2/rman_backup/level0 >> /database/backup2/backup_tape/level0_rman_06sep12 2>&1;
from the log i got the error
bash# tail -f level0_rman_06sep12
DUMP: Date of... (3 Replies)
I am trying to learn C and while trying out some code, the program is getting aborted while I am calling free().
Here is the code:
#include <stdlib.h>
#include <stdio.h>
void print_by_ptr(char **str) {
printf("<%s>\n",*str);
printf("Now I am modifying the str.\n");
*str =... (3 Replies)
Discussion started by: chacko193
3 Replies
LEARN ABOUT MOJAVE
dup3
DUP(2) Linux Programmer's Manual DUP(2)NAME
dup, dup2, dup3 - duplicate a file descriptor
SYNOPSIS
#include <unistd.h>
int dup(int oldfd);
int dup2(int oldfd, int newfd);
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <fcntl.h> /* Obtain O_* constant definitions */
#include <unistd.h>
int dup3(int oldfd, int newfd, int flags);
DESCRIPTION
The dup() system call creates a copy of the file descriptor oldfd, using the lowest-numbered unused file descriptor for the new descriptor.
After a successful return, the old and new file descriptors may be used interchangeably. They refer to the same open file description (see
open(2)) and thus share file offset and file status flags; for example, if the file offset is modified by using lseek(2) on one of the file
descriptors, the offset is also changed for the other.
The two file descriptors do not share file descriptor flags (the close-on-exec flag). The close-on-exec flag (FD_CLOEXEC; see fcntl(2))
for the duplicate descriptor is off.
dup2()
The dup2() system call performs the same task as dup(), but instead of using the lowest-numbered unused file descriptor, it uses the file
descriptor number specified in newfd. If the file descriptor newfd was previously open, it is silently closed before being reused.
The steps of closing and reusing the file descriptor newfd are performed atomically. This is important, because trying to implement equiv-
alent functionality using close(2) and dup() would be subject to race conditions, whereby newfd might be reused between the two steps.
Such reuse could happen because the main program is interrupted by a signal handler that allocates a file descriptor, or because a parallel
thread allocates a file descriptor.
Note the following points:
* If oldfd is not a valid file descriptor, then the call fails, and newfd is not closed.
* If oldfd is a valid file descriptor, and newfd has the same value as oldfd, then dup2() does nothing, and returns newfd.
dup3()
dup3() is the same as dup2(), except that:
* The caller can force the close-on-exec flag to be set for the new file descriptor by specifying O_CLOEXEC in flags. See the description
of the same flag in open(2) for reasons why this may be useful.
* If oldfd equals newfd, then dup3() fails with the error EINVAL.
RETURN VALUE
On success, these system calls return the new file descriptor. On error, -1 is returned, and errno is set appropriately.
ERRORS
EBADF oldfd isn't an open file descriptor.
EBADF newfd is out of the allowed range for file descriptors (see the discussion of RLIMIT_NOFILE in getrlimit(2)).
EBUSY (Linux only) This may be returned by dup2() or dup3() during a race condition with open(2) and dup().
EINTR The dup2() or dup3() call was interrupted by a signal; see signal(7).
EINVAL (dup3()) flags contain an invalid value.
EINVAL (dup3()) oldfd was equal to newfd.
EMFILE The per-process limit on the number of open file descriptors has been reached (see the discussion of RLIMIT_NOFILE in getrlimit(2)).
VERSIONS
dup3() was added to Linux in version 2.6.27; glibc support is available starting with version 2.9.
CONFORMING TO
dup(), dup2(): POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
dup3() is Linux-specific.
NOTES
The error returned by dup2() is different from that returned by fcntl(..., F_DUPFD, ...) when newfd is out of range. On some systems,
dup2() also sometimes returns EINVAL like F_DUPFD.
If newfd was open, any errors that would have been reported at close(2) time are lost. If this is of concern, then--unless the program is
single-threaded and does not allocate file descriptors in signal handlers--the correct approach is not to close newfd before calling
dup2(), because of the race condition described above. Instead, code something like the following could be used:
/* Obtain a duplicate of 'newfd' that can subsequently
be used to check for close() errors; an EBADF error
means that 'newfd' was not open. */
tmpfd = dup(newfd);
if (tmpfd == -1 && errno != EBADF) {
/* Handle unexpected dup() error */
}
/* Atomically duplicate 'oldfd' on 'newfd' */
if (dup2(oldfd, newfd) == -1) {
/* Handle dup2() error */
}
/* Now check for close() errors on the file originally
referred to by 'newfd' */
if (tmpfd != -1) {
if (close(tmpfd) == -1) {
/* Handle errors from close */
}
}
SEE ALSO close(2), fcntl(2), open(2)COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project, information about reporting bugs, and the
latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.
Linux 2017-09-15 DUP(2)