Determine the fork and execlp functions - linux, Operating System

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  • In this example, when you call make target, the make program checks if any of the dependencies of target are out of date.
  • If one or more of them is out of date, the command to execute is run.
Posted Date: 3/4/2013 6:41:52 AM | Location : United States







Related Discussions:- Determine the fork and execlp functions - linux, Assignment Help, Ask Question on Determine the fork and execlp functions - linux, Get Answer, Expert's Help, Determine the fork and execlp functions - linux Discussions

Write discussion on Determine the fork and execlp functions - linux
Your posts are moderated
Related Questions
Q. Discuss the advantages as well as disadvantages of caching name translations for computers located in remote domains. Answer: There is a performance benefit to caching nam

Q. Segmentation is alike to paging but uses variable-sized "pages". Describe two segment-replacement algorithms based on FIFO and LRU page replacement schemes. Remember that since


#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

Placement algorithms :calculate where in available real-memory to execute a program. Common functions are next-fit, first-fit, and best-fit. Replacement algorithms :are

server configure

explain how response time are reduced by allowing time sharing on top of multiprogramming

What is the main advantage of the layered approach to system design? As in all cases of modular design, designing an operating system in a modular way has several benefits. Th

What are the characteristics of SRS? i. Correct - The SRS should be made up to date when appropriate requirements are identified. ii. Unambiguous - When the requirements are

explain about design issues of network operating system