I tried using the following code to execute a program but it doesnt seems to be working .. I would like to know whats wrong wit it .
execve("/bin/cat", "words", NULL); (0 Replies)
Hi,
Program A: uses pipe()
I am able to read the stdout of PROGAM B (stdout got through system() command) into PROGRAM A using:
* child
-> dup2(fd, STDOUT_FILENO);
-> execl("/path/PROGRAM B", "PROGRAM B", NULL);
* parent
-> char line;
-> read(fd, line, 100);
Question:... (2 Replies)
hello everybode.Got some sort of "problems" with this stuff;
well this is a program
int main()
{
int Pipe;
int origStdin, origStdout;
int childPID;
origStdin = dup(0);
origStdout = dup(1);
pipe(Pipe);
if( (childPID = fork()) < 0 )
{
perror(... (2 Replies)
Hi,
I'm writing a monitor program that can be notified once a process makes an execve system call and then stop that process for examining before it starts to run the new code. I know I can ptrace a process to achieve this, but I do not want to ptrace every process in the system. Is it possible?... (1 Reply)
Disclaimer: This is just a rainy day experiment. There is no expected "goal" other than to understand UNIX better.
After reading about fork and exec, my understanding is that forking, as the UNIX shell does by design, consequentially may sacrafice some speed versus an approach that runs in... (1 Reply)
Hello everybody.I want to make clear that i am not going to ask from anybody to build my asignement but i have a big problem. I can't seem to find anywhere ONE good example on C about what i am trying to do:wall:.I think it is simple. All i ask is one example, even a link is fine.
So, i want to... (1 Reply)
Hi guys,
I need to know how i can ignore Pipe '|' if Pipe is coming as a column in Pipe delimited file
for eg:
file 1:
xx|yy|"xyz|zzz"|zzz|12...
using below awk command
awk 'BEGIN {FS=OFS="|" } print $3
i would get xyz
But i want as :
xyz|zzz to consider as whole column... (13 Replies)
Hi,
I have the following scenario..
1) I have a binary which i launch from command line. It executes fine.
2) But when I launch it from another file using execve command, it gives a message that it is not able to access a shared object ".so" in /usr/bin (message is "Permission... (4 Replies)
The task I have to do is something along the lines "I receive some input and based on the first character I send it through pipe to one of the children to print".
The scheme it is based on is 1->2; 1->3; 1->4; 2 will print all the input that starts with a letter, 3 will print all the input that... (2 Replies)
Discussion started by: Ildiko
2 Replies
LEARN ABOUT OSX
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 execve(2), fork(2), sigaction(2), wait(2)ERRORS
The vfork() system call will fail for any of the reasons described in the fork man page. In addition, it will fail if:
[EINVAL] A system call other than _exit() or execve() (or libc functions that make no system calls other than those) is called fol-
lowing calling a vfork() call.
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