I'm having problems with pipes... I need comunnications with childs processes and parents, but only one child can comunnicate with parent (first child), others childs can't.
A brief of code:
Results are:
First pipe (client1r) works correctly, but others pipe (client2r and client3r) doesn't works. I don't understant why doesn't works, because others pipes are exactly the same, and then I call another function (function client) passin the value.
I have a one line bat script run off a XP machine that tar's and compresses some files from a Sol 8 box. It goes something like this (a bit simplified)....
plink -pw <passwd> user@host "tar -cvf - -C / tmp/a_file | compress " > a_file.tar.Z
So this works....and it's worked many times. But now... (3 Replies)
I have written the following program. The function of this prog is to read data from a file(source.c) and write into another file(dest.c) using pipes. I have just written a line in the source file.Im able to compile and run the program without errors. But the data is not written onto the other... (2 Replies)
Could anyone tell me whats wrong whit this piping? the commands that they execute are correct. the command I am trying is ls|wc. Both processes go to the right if statement.
for(i=0;i<argc;i++){
if(i==0&&argc>1){//first command
if(pipe(pipa1)==-1)
... (2 Replies)
1. The problem statement, all variables and given/known data:
I have two files created from extracting data off of two CSV files, one containing class enrollment on a specific quarter and the other containing grades for that specific quarter. The Enrollment file generated contains course name,... (11 Replies)
Here is an example code that shows the issue I have:
#!/bin/bash
counter() {
seq 1000 | while read NUM; do
echo $NUM
echo "debug: $NUM" >&2
sleep 0.1 # slow it down so we know when this loop really ends
done
}
counter | grep --line-buffered "" | head -n1
... (10 Replies)
I'm using Sendmail 8.13.8 on a CentOS 5.5 vServer (Virtuozzo).
I'm using a loop in PHP to send a lot of HTML-mails via sendmail. Each mail is a mail with individual statistics for our users, so its not mass mailing, bcc is not an option.
It all works fine, but when I take a closer look there... (2 Replies)
Hi,guys:
I want to use c to implement a pipe. For example:
ps auxwww | grep fred | more
I forked three child processes. Each is responsible for each command, and pipe to next one.
for(i=0;i<2;i++)
pipe(fd)
if(child==1) // child 1
{
close(1)
dup2(fd,1)
close(fd)
}... (3 Replies)
I want to have a message send & receive through 2 half-duplex pipes
Flow of data
top half pipe
stdin--->parent(client) fd1--->pipe1-->child(server) fd1
bottom half pipe
child(server) fd2---->pipe2--->parent(client) fd2--->stdout
I need to have boundary structed message... (1 Reply)
Discussion started by: ouou
1 Replies
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