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  • In this example, when you call make target, the make program checks if any of the dependencies of target are out of date.
  • If one or more of them is out of date, the command to execute is run.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

Write note on process, Write note on process, process state? A process ...

Write note on process, process state? A process is in excess of the program code which is sometimes known as text section. It as well includes the current activity as represent

Paging, protection in paging

protection in paging

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

Write a short note on memory management, Write a short note on Memory manag...

Write a short note on Memory management. Memory management includes reallocating and allocating the memory space. The kinds of allocation of memory FIXED PARTITIONING

Explain file control list and user control list, Q. Researchers have recom...

Q. Researchers have recommended that instead of having an access list associated with each file (specifying which users can access the file and how) we should have a user control

Explain tightly coupled systems and loosely coupled system, Differentiate t...

Differentiate tightly coupled systems and loosely coupled systems? Loosely coupled systems:-  Every processor has its own local memory  Every processor can communicate

Batch oriented and interactive operating system., properies of Batch orient...

properies of Batch oriented and interactive operating system.

Inter-process Communication !, My code it didn''t run properly ,i tried to ...

My code it didn''t run properly ,i tried to pass 2 parameter example : ./a.out ls -ll ,but it execute only the ls instead of the ls -ll ! plz help amd thank you ! #include #inclu

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