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  • In this example, when you call make target, the make program checks if any of the dependencies of target are out of date.
  • If one or more of them is out of date, the command to execute is run.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

What are the three major purposes of an operating system, Q. What are the t...

Q. What are the three major purposes of an operating system? Answer: To offers an environment for a computer user to execute programs on computer hardware in a conveni

Explain concept of buffering, Buffering Messages exchanged by communica...

Buffering Messages exchanged by communication processes reside in a impermanent queue. Such a queue can be executed in three ways. Zero capacity: The queue length is 0.

What do you mean by reference counts, Q. If each the access rights to an o...

Q. If each the access rights to an object are deleted the object can no longer be accessed. At this stage the object should also be deleted and the space it occupies should be ret

What are the benefits of multiprogramming?, What are the benefits of multip...

What are the benefits of multiprogramming? Responsiveness : Multithreading is an interactive application may permit a program to continue running even if part of it is block

Model, list trhe various classification of model and types?

list trhe various classification of model and types?

#network OS, what are the design issues of network OS

what are the design issues of network OS

Operational management, explain the link between operations management and ...

explain the link between operations management and strategic planning of daily goods shop

Explain the real time operating system, Explain the Real Time Operating Sys...

Explain the Real Time Operating System A real-time operating system comprises definite, fixed time constraints. Processing should be done in the defined constraints, or the sys

Explain a working of file control block, Explain a working of file control ...

Explain a working of file control block A file control block (FCB) has information about the file, containing ownership, permission, and location of the file contents. The log

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