01-03-2008
Quote:
Originally Posted by
porter
fork and exec are two of the most fundamental calls on a UNIX system, if these are failing the system won't work.
Any alternative, such as "system()" or "popen()" will call fork()/vfork() and exec(), there is not really any other portable way to start a new process and launch a new program in it.
I suggest the errors are in the usage or understanding of what these calls do.
Admittedly, Linux has clone() but that's another story.
Thanks porter for your reply. The problem is not exactly in usage because it is running at few machines too. It may be some sort of environment or previledges problem. Actually now the situation is that I am trying to do that using Multithreading. I am creating two threads.
I needed to call an executable with some arguments in the function body for second thread. For that I am using system() call.
The problem is that :-
1. system() function call is not allowing any further arguments to executable being called as execl() would if I was using a fork()-execl() pair in case of Multiprocessing.
2. I need alternative to system() because system is also creating a new process. And I dont want to create a new process in a thread.
Regards,
Raj Kumar Arora
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LEARN ABOUT OPENDARWIN
vfork
VFORK(2) BSD System Calls Manual VFORK(2)
NAME
vfork -- spawn new process in a virtual memory efficient way
SYNOPSIS
#include <unistd.h>
pid_t
vfork(void);
DESCRIPTION
Vfork() can be used to create new processes without fully copying the address space of the old process, which is horrendously inefficient in
a paged environment. It is useful when the purpose of fork(2) would have been to create a new system context for an execve. Vfork() differs
from fork in that the child borrows the parent's memory and thread of control until a call to execve(2) or an exit (either by a call to
exit(2) or abnormally.) The parent process is suspended while the child is using its resources.
Vfork() returns 0 in the child's context and (later) the pid of the child in the parent's context.
Vfork() can normally be used just like fork. It does not work, however, to return while running in the childs context from the procedure
that called vfork() since the eventual return from vfork() would then return to a no longer existent stack frame. Be careful, also, to call
_exit rather than exit if you can't execve, since exit will flush and close standard I/O channels, and thereby mess up the parent processes
standard I/O data structures. (Even with fork it is wrong to call exit since buffered data would then be flushed twice.)
SEE ALSO
fork(2), execve(2), sigaction(2), wait(2),
DIAGNOSTICS
Same as for fork.
BUGS
This system call will be eliminated when proper system sharing mechanisms are implemented. Users should not depend on the memory sharing
semantics of vfork as it will, in that case, be made synonymous to fork.
To avoid a possible deadlock situation, processes that are children in the middle of a vfork() are never sent SIGTTOU or SIGTTIN signals;
rather, output or ioctl(2) calls are allowed and input attempts result in an end-of-file indication.
HISTORY
The vfork() function call appeared in 3.0BSD.
4th Berkeley Distribution June 4, 1993 4th Berkeley Distribution