Determine the fork and execlp functions - linux, Operating System

Assignment Help:

Assignment

  • What I'm covering:
  • General control flow
  • fork()
  • execlp()
  • Parameters
  • Makefiles
  • Additional Questions

General Control Flow/fork()

  • In the Controller:

int main(int argc,char** argv){

.....

for(i = 0;i < 4;i++){

int ret_pid = fork();

if ( ret_pid < 0 ) exit(1); //this means fork() failed

else if ( ret_pid == 0 ) !  //this is the child

else ...  //this is the parent (Controller)

}

return 0;

}

 

execlp()

  • This function call has a lot of gotchas that look very confusing at first glance.
  • The first argument to execlp is the string with the file name that will be executed...and so is the second.
  • Think about your own program being called from the command-line ( > ./a.out arg1 arg2 ). In this case, the value of argv[0] in the program is "a.out".

Same thing applies when using exec, you just have to be explicit about it.

 

More execlp() and parameters

  • The rest of the parameters to execlp are strings containing the rest of the arguments, in our case, the numbers that the calculator will be operating on.
  • These will be passed to Controller as arguments, and from there, they will be passed to Calculator.
  • No matter what, the last argument to execlp MUST be a null-terminator (NULL or (char*) 0).

This is because the argument list must be null-terminated, just like any other string.

 

Makefiles

  • This assignment requires that TWO executables be created: the Controller and the Calculator.
  • Because of how Eclipse generates its makefiles, if you try to do this in a single project, Eclipse will whine. I recommend doing your coding in a normal text editor (gedit, emacs, vi, bluefish, etc.), and writing your own makefile.
  • There are plenty of makefile tutorials online; but this project (and the next one) will not require a particularly complex makefile.

 

Makefile example

  • Here's the general format of a makefile entry:

[target] : [dependency1] ! [dependencyn] [command to execute]

  • In this example, when you call make target, the make program checks if any of the dependencies of target are out of date.
  • If one or more of them is out of date, the command to execute is run.

Related Discussions:- Determine the fork and execlp functions - linux

Process states in linux, Process states in Linux OS Running:  Process ...

Process states in Linux OS Running:  Process is either ready to run or running Interruptible:  a Blocked part of a process and waiting for a signal or an event from anothe

Galvin, difference between process and thread

difference between process and thread

Define process swapping , Swapping : Whole process is moved from the swap...

Swapping : Whole process is moved from the swap machine to the main memory for execution. Process size must be equal or less than to the used main memory. It is easier to exe

Explain single partition allocation., Operating Systems 1. Explain sing...

Operating Systems 1. Explain single Partition Allocation and Multiple Partition Allocation. 2. What do you mean by PCB? What useful information is available in PCB? 3. De

Illustrate the function of loader, Q. Illustrate the function of Loader? ...

Q. Illustrate the function of Loader? A loader is a routine which loads an object program and prepares it for execution. There are many loading schemes: relocating, absolute an

Intranet, how intranet can make your business effective

how intranet can make your business effective

Removing system dependencies, Removing System Dependencies Because port...

Removing System Dependencies Because portions of the client - server application program may execute on different machines, it is very important for the developer to remove the

Semantics for execution of rpcs, Q. Presume that a distributed system is su...

Q. Presume that a distributed system is susceptible to server failure. What mechanisms would be needed to guarantee the exactly once semantics for execution of RPCs? Ans

What are the objectives for a file management system, What are the objectiv...

What are the objectives for a file management system? To meet the data management wants and requirements of the user, which embrace storage of data and the ability to

Linux, how to find ncr value in shell script

how to find ncr value in shell script

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd