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  • In this example, when you call make target, the make program checks if any of the dependencies of target are out of date.
  • If one or more of them is out of date, the command to execute is run.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

Explain how protection is provided for the hardware resource, Explain how p...

Explain how protection is provided for the hardware resources by the operating system. Dual mode operation Sharing system resources needs operating system to make sure

Explain disk scheduling algorithms-shortest seek time first, SSTF (Shortest...

SSTF (Shortest Seek Time First) After a demand go to the closest request in the work queue regardless of direction Decrease total seek time compared to FCFS Disadv

Why high level languages need compiler, Q. Why High level languages need Co...

Q. Why High level languages need Compiler? High level languages - illustrations are COBOL, FORTRAN, PL/I andALGOL - are processed by interpreters andcompilers. A compilers is a

Explain the performance of demand paging, Performance of demand paging ...

Performance of demand paging Demand paging can have an important effect on the performance of a computer system. As long as there are no page faults, the effective access time

Important system components, Organizational, Structural, Logical and Execut...

Organizational, Structural, Logical and Execution Relationships Between Important System Components in Linux Kernel Subsystems A. Description of the Project You are require

Explain kernel-level threads (klt), KERNEL-LEVEL THREADS (KLT) In this...

KERNEL-LEVEL THREADS (KLT) In this level every thread management is done by kernel .No thread library except an API system calls to the kernel thread facility exists. The kern

Explain the architecting for threads, Explain the Architecting For Threads ...

Explain the Architecting For Threads When available, threads are an integral part of any multitasking server application program. It is important that the operating system prov

Explain about system software, An operating system act as an intermediary b...

An operating system act as an intermediary between user of a computer and computer hardware. The objective of an operating system is to provide an environment in that a user can ex

Search and print between two words/patterns, what if we need the portion fr...

what if we need the portion from a text based on some keyword. For eg. My file is like below, ------------------------------------------------ Order=[ 1 2 3 4 5 Order=[ 6 7 8 9

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