What this code should do is: there are parent.cpp and child.cpp. Parent will send whatever is in the buffer to child and child will send back whatever received to parent. I do not know what I am doing wrong. I am confused what is missing in the parent and what else I should include into the child. Thanks.
I have been busy reading away on devices and filesystems and I am stuck on a particular subject matter.. I'm not understanding the concept behind mknod mkfifo makedev or related commands..
can anyone shed some light on the subject.!
any feedback welcome!
moxxx68 (0 Replies)
I'm having difficulty understanding the purposes of using dup/dup2 when involving forks.
for example, if we call fork() once, that is, we are creating a child process. In what cases would we need to use dup or dup2 to duplicate the file descriptors for standard output and standard error? What... (1 Reply)
I want to search for the line with the group name and add the user into the group. The file format is the same as /etc/group
The code i wrote is
egrep "^$newGID" $group >/dev/null
FS=":"
oldData=awk -F: '{print $3}'
newData= "$oldData,$newUser"
sed -n $4/$newData $group
but a friend... (1 Reply)
Hi,
i have in one program such a pice of code
................
static int old_stderr_handle = -1;
static int old_stdout_handle = -1;
log_handle = open(log_file_name,O_CREAT|O_RDWR,932);
old_stderr_handle = dup(STDERR_FILENO);
if (dup2(log_handle,STDERR_FILENO) < 0)
{
//... (1 Reply)
int redirect()
{
int fd,rc;
fd = open("sample.DAT",O_CREAT | O_RDWR , 00777 );
rc = dup2(fd , 1 ) ;
close (fd );
return 0;
}
I used the above to redirect all the cout statements to sample.DAT. process is redirecting the output and I had two questions
1. All stdout/cout statements... (2 Replies)
Hi all,I'm reading <Advanced programming in the UNIX environment>,that book asked the reader to implement a function which has same functions with dup2 without calling fcntl.Could anyone give me a tip?Any help will be appreciated.:) (8 Replies)
is it possible to duplicate file descriptors(opened by a different process) with the help of dup or dup2. the two process do not share parent child relationship as well. (2 Replies)
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)
I want to execute metasploit by two pipes to communicate with it, but I have troubles with that communication. When I run my program, I get this error: "stty: standard input: Inappropriate ioctl for device" and I don't receive the metasploit promt.
just select an exploit.
This is my code:... (2 Replies)
Discussion started by: dano88
2 Replies
LEARN ABOUT HPUX
vfork
vfork(2) System Calls Manual vfork(2)NAME
vfork - spawn new process; share virtual memory
SYNOPSIS REMARKS
is a higher performance version of that is provided on some systems where a performance advantage can be attained.
If the calling process is multi-threaded, the newly created child process will only contain one thread. This one thread will be a copy of
the thread calling
differs from only in that the child process can share code and data with the calling process (parent process). This speeds cloning activ-
ity significantly at a risk to the integrity of the parent process if is misused.
The use of for any purpose except as a prelude to an immediate or is not supported. Any program that relies upon the differences between
and is not portable across HP-UX systems.
All HP-UX implementations must provide the entry but it is permissible for them to treat it identically to On some implementations the two
are not distinguished because the implementation is as efficient as possible. Other versions may do the same to avoid the overhead of sup-
porting two similar calls.
DESCRIPTION
can be used to create new processes without fully copying the address space of the old process. If a forked process is simply going to do
an (see exec(2)), the data space copied from the parent to the child by is not used. This is particularly inefficient in a paged environ-
ment, making particularly useful. Depending upon the size of the parent's data space, can give a significant performance improvement over
differs from in that the child borrows the parent's memory and thread of control until a call to or an exit (either by a call to or abnor-
mally (see exec(2) and exit(2)). The parent process is suspended while the child is using its resources.
returns 0 in the child's context and (later) the pid of the child in the parent's context.
can normally be used just like It does not work, however, to return while running in the child's context from the procedure which called
since the eventual return from would then return to a no longer existent stack frame.
The window begins at the call and ends when the child completes its call.
RETURN VALUE
Upon successful completion, returns a value of 0 to the child process and returns the process ID of the child process to the parent
process. Otherwise, a value of -1 is returned to the parent, no child process is created, and is set to indicate the error.
ERRORS
fails and no child process is created if any of the following conditions are encountered:
The system-wide limit on the total number of processes under execution
would be exceeded.
The system-imposed limit on the total number of processes under execution
by a single user would be exceeded.
DEPENDENCIES
Servers
Process times for the parent and child processes within the window may be inaccurate.
Parent and child processes share the same stack space within the window. If the size of the stack has been changed within this win-
dow by the child process (return from or call to a function, for example), it is likely that the parent and child processes will be
killed with signal or
In the window, a call to (see signal(2) that installs a catching function can affect handling of the signal by the parent. The par-
ent is not affected if the handling is being set to or or if is used (see sigaction(2)).
AUTHOR
was developed by the University of California, Berkeley.
SEE ALSO exec(2), exit(2), fork(2), sigaction(2), wait(2).
vfork(2)