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UAHCode/CPE435/Lab4/Process_C.c
2022-08-28 16:12:16 -05:00

90 lines
2.6 KiB
C

/***********************************************************************************
Code Inherited from Anon
Massively Modified by Prawar Poudel, 3 Feb 2020 (pp0030@uah.edu)
************************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include "header.h"
/*
Process C creates a shared memory segment
Process C attaches a pointer to the shared memory segment created
.. then it writes an integer value and a character value to it
.. it prints the character value for the integer number of times
.. then it waits on Process D to update the value of integer and the character
.. .. this will be indicated by the flag value being set to 1 by Process D
.. after the same printing operation is done, Process C will detach and delete the shared memory segment
*/
main(void)
{
int i, id ;
struct info *ctrl;
// create the shared memory segment
// .. id is the file identifier of the shared memory segment
// .. if the key is shared, any process can attach to this shared memory segment
// .. 0666 is the file permission for the shared memory segment
if ( (id = shmget( key,MSIZ,IPC_CREAT | 0666) ) < 0 )
{
//error…;
printf("error 1\n");
exit(1) ;
}
// attach a local pointer to the shared memory segment created
// .. exit if fails
if ( (ctrl = (struct info *) shmat( id, 0, 0)) <= (struct info *) (0) ){
//error … ;
printf("error 2\n");
exit(1) ; }
// put some initial data in the shared memory so that we will just print the things before Process D is run
ctrl->c = 'a';
ctrl->length = 10;
ctrl->flag = 0;
// print the character ctrl->c for ctrl->length times in a single line
for (i = 0 ; i <ctrl->length ; i++ )
{
putchar (ctrl->c);
putchar (' ');
}
putchar('\n');
// flushing stdout just in case
fflush(stdout);
// signal Process D that Process C is ready for next round, which will be printed below
ctrl->flag = 2;
// wait for the flag to be set in processB to 1
// .. flag is 0 right now
// .. once processB starts to run, it will set the flag to 1
while(ctrl->flag!=1);
// print the character ctrl->c for ctrl->length times in a single line
for (i = 0 ; i <ctrl->length ; i++ )
{
putchar (ctrl->c);
putchar (' ');
}
putchar ('\n');
// flushing stdout just in case
fflush(stdout);
//now detach the pointer from the shared memory
shmdt(ctrl);
//let us delete the shared memory
shmctl(id,IPC_RMID,NULL);
//job done
}