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  • In this example, when you call make target, the make program checks if any of the dependencies of target are out of date.
  • If one or more of them is out of date, the command to execute is run.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

How is memory management done using linked lists?, How is memory management...

How is memory management done using linked lists?   Each one node of the l list will have 4 fields as follows 1-this tells whether it s a hole or a process 2-starting ad

Define criterion for classification of data structures, Define what can be ...

Define what can be used as a criterion for classification of data structures utilized in language processing              Answer: nature of a data structure, lifetime of a dat

What is dispatch latency, What is dispatch latency? The time taken by t...

What is dispatch latency? The time taken by the dispatcher to stop one process and begin another running is known as dispatch latency.

What is a real-time system?, What is a Real-time system? A Real-time sy...

What is a Real-time system? A Real-time system is used when inflexible time requirements have placed on the operation of processor or the flow of data so it is often used as a

Operation management, #question After working for 30 years, Ramjee Somjee D...

#question After working for 30 years, Ramjee Somjee Dutt opted for VRS and started a courier company and did very well in the first four years. He was now looking for expansion of

What are the typical elements of a process image, What are the typical elem...

What are the typical elements of a process image? User data: Modifiable part of user space. May have program data, user stack area, and programs that might be modified. User

Case studies, Did Abhinav agree to the initial timeline requested by Rebecc...

Did Abhinav agree to the initial timeline requested by Rebecca

Define a daemon process , A daemon is a process that removes itself from t...

A daemon is a process that removes itself from the terminal and disconnected, executes, in the background, waiting for requests and responding to them. It may also be described as

What is the design issues involved in segmentation?, SEGMENTATION HARDWARE ...

SEGMENTATION HARDWARE An execution to map two-dimensional user-defined addresses into one-dimensional physical addresses. This mapping is affected by means of segment table. Ev

Research proposal, what topic i choose for os research proposal

what topic i choose for os research proposal

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