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  • In this example, when you call make target, the make program checks if any of the dependencies of target are out of date.
  • If one or more of them is out of date, the command to execute is run.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

Linux kernel components, Example 1.  The diagram illustrating the data stru...

Example 1.  The diagram illustrating the data structures of in-memory VFS objects and on-disk objects and their relationships on slide 24 of the lecture notes OSD.4. This diagram i

Develop the material requirements plan, The following information is availa...

The following information is available for three MPS (Master Product Scheduling) items: Product A                            An 80 unit order is to be started in Week 3.

Define virtual memory, Define Virtual memory Virtual memory is employe...

Define Virtual memory Virtual memory is employed in all major commercial operating systems

Write a short note on file organization and access, Write a short note on f...

Write a short note on file organization and access. There are three methods to access files 1Record Access 2Sequential Access 3Random Access The record access

Operation research, scattered resposibi;ity and authority -necessity of ope...

scattered resposibi;ity and authority -necessity of operation research

What are the issues in designing a network-scalability, Scalability : ...

Scalability : Scalability is the competence of the system to adapt to increased service load. A scalable system will respond more gracefully to increased load than a non-sc

Virtual addresses, Virtual addresses are made up of two parts: the ?rst par...

Virtual addresses are made up of two parts: the ?rst part is the page number, and the second part is an offset inside that page. Suppose our pages are 4kb (4096 = 212 bytes) long,

Can we call trap as an interrupt??, is there any difference between the tra...

is there any difference between the trap and interrupt??

Explain acyclic-graph directories, Acyclic-graph directories An acyclic...

Acyclic-graph directories An acyclic graph permits directories to have shared subdirectories and files. The similar file or subdirectory may be in two dissimilar directories. A

Explain threads for executing concurrent application code, Explain Threads ...

Explain Threads for Executing Concurrent Application Code The thread has been introduced in many operating systems as an efficient mechanism for executing concurrent applicatio

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