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Newbie question on exec,fork, wait,pipe C
Post 302527708 by Cuervo on Saturday 4th of June 2011 06:27:43 PM
06-04-2011
Newbie question on exec,fork, wait,pipe C
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
.I think it is simple. All i ask is one example, even a link is fine.
So, i want to make a program (Grandfather.c) which will run 2 new existing programs (Father.c,Son.c). Father.c needs to make some calculations.He wakes up Son.c.He sends him two numbers and Son.c adds them and sends back the result.After this Son.c sleeps.
So,to sum up:
1.Grandfother.c runs the 2 programs
2.Son.c builds the pipes and falls asleep
3.Father.c wakes his son and sends him 2 numbers and falls asleep
4.Son.c adds the numbers, sends them back and falls asleep again
I have found several examples that use functions in one program,but i don't understand how to establish connection in 3 programs.Thnak you in advance!!
.I think it is simple. All i ask is one example, even a link is fine.So, i want to make a program (Grandfather.c) which will run 2 new existing programs (Father.c,Son.c). Father.c needs to make some calculations.He wakes up Son.c.He sends him two numbers and Son.c adds them and sends back the result.After this Son.c sleeps.
So,to sum up:
1.Grandfother.c runs the 2 programs
2.Son.c builds the pipes and falls asleep
3.Father.c wakes his son and sends him 2 numbers and falls asleep
4.Son.c adds the numbers, sends them back and falls asleep again
I have found several examples that use functions in one program,but i don't understand how to establish connection in 3 programs.Thnak you in advance!!
Last edited by Cuervo; 06-04-2011 at 09:10 PM..
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LEARN ABOUT V7
fork
FORK(2) System Calls Manual FORK(2) NAME
fork - spawn new process SYNOPSIS
fork( ) DESCRIPTION
Fork is the only way new processes are created. The new process's core image is a copy of that of the caller of fork. The only distinc- tion is the fact that the value returned in the old (parent) process contains the process ID of the new (child) process, while the value returned in the child is 0. Process ID's range from 1 to 30,000. This process ID is used by wait(2). Files open before the fork are shared, and have a common read-write pointer. In particular, this is the way that standard input and output files are passed and also how pipes are set up. SEE ALSO
wait(2), exec(2) DIAGNOSTICS
Returns -1 and fails to create a process if: there is inadequate swap space, the user is not super-user and has too many processes, or the system's process table is full. Only the super-user can take the last process-table slot. ASSEMBLER
(fork = 2.) sys fork (new process return) (old process return, new process ID in r0) The return locations in the old and new process differ by one word. The C-bit is set in the old process if a new process could not be cre- ated. FORK(2)