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<html> <head><title>Examples for /home/faculty/sprenkle/public_html/cs330/examples/12-ipc</title> <link rel="stylesheet" type="text/css" href="http://www.cs.wlu.edu/~sprenkle/cs330/assignments/assign.css" /> </head> <body> <h1>Examples for /home/faculty/sprenkle/public_html/cs330/examples/12-ipc</h1> <ul> <li><a href=".//code.html">All IN ONE FILE (pretty syntax)</a> <li><a href=".//a.out">a.out</a></li> <li><a href=".//pipedemo.c">pipedemo.c</a></li> <li><a href=".//sharedmem.c">sharedmem.c</a></li> </ul> </body>
/*
* Demonstration of how to create and use an Unnamed
* Unix pipe to communicate between a parent and a
* child.
*/
#include <stdio.h> // for printf
#include <unistd.h> // for fork & pipe stuff.
#include <sys/wait.h> // for wait
#define READ_END 0
#define WRITE_END 1
int main() {
printf("Parent running\n");
// Create the pipe before the fork so that the child
// process has a copy of it after the fork.
int fd[2];
if (pipe(fd) == -1) {
printf("Pipe creation failed\n");
return -1;
}
// Create child process.
int pid = fork();
// fork returns pid of child process in parent
// and 0 in the child.
if (pid != 0) {
printf("Parent running after fork\n");
// The parent will write to the pipe. So close
// the read end of the pipe and begin writing data.
close(fd[READ_END]);
char *str1 = "printing to the pipe.\0";
char *str2 = "putting more in pipe.\0";
printf("Parent writing: %s\n", str1);
write(fd[WRITE_END], str1, 21);
sleep(3);
printf("Parent writing: %s\n", str2);
write(fd[WRITE_END], str2, 21);
close(fd[WRITE_END]);
printf("Parent done\n");
}
else {
printf("Child running\n");
// The child will read from the pipe. So close the
// write end of the pipe and begin reading until the
// parent closes the pipe.
close(fd[WRITE_END]);
char buf[1];
while(read(fd[READ_END], buf, 1) != 0) {
printf("%s\n",buf);
}
close(fd[READ_END]);
printf("Child done\n");
}
}
#include <stdio.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/wait.h>
int main() {
int segID;
// Create 4 bytes of shared memory. Just enough for one int value.
segID = shmget(IPC_PRIVATE, 4, S_IRUSR | S_IWUSR);
int pid = fork();
if (pid != 0) {
// Get a pointer to the shared bytes for the parent.
int *sharedInt = (int *) shmat(segID, NULL, 0);
// forced yield of the process
//sleep(1);
// Store the value 7 in the shared space.
sharedInt[0] = 7;
printf("Parent Before: %d\n", sharedInt[0]);
wait(NULL);
printf("Parent After: %d\n", sharedInt[0]);
}
else {
// Get a pointer to the shared bytes for the child.
int *sharedInt = (int *) shmat(segID, NULL, 0);
printf("Child Before: %d\n", sharedInt[0]);
// Change the value stored in the shared space.
sharedInt[0] = 9;
printf("Child After: %d\n", sharedInt[0]);
}
}