55 lines
1.4 KiB
C
55 lines
1.4 KiB
C
/*
|
|
* ipcsfs1 - Using the file system for inter-process communication
|
|
* Shows a problem with the fact that the file position
|
|
* pointer is shared between parent and child
|
|
*/
|
|
|
|
#include <fcntl.h> // needed for open system call
|
|
#include <stdio.h> // needed for printf
|
|
#include <stdlib.h> // needed for exit
|
|
#include <string.h> // nneded for strlen
|
|
#include <sys/types.h> // needed for pid_t
|
|
#include <sys/wait.h> // needed for wait system call
|
|
#include <unistd.h> // needed for fork, read, write, close system calls
|
|
|
|
int main()
|
|
{
|
|
// Open a file for reading and writing
|
|
// Create it if it doesn't exist
|
|
int myfile = open("MYFILE", O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
|
|
|
|
pid_t pid = fork(); // fork into 2 processes
|
|
|
|
if (pid < 0) // error
|
|
{
|
|
printf("ERROR: COULD NOT FORK\n");
|
|
exit(EXIT_FAILURE);
|
|
}
|
|
else if (pid == 0) // child
|
|
{
|
|
/* Write to parent */
|
|
char *data = "HELLO";
|
|
write(myfile, data, strlen(data));
|
|
printf("Child wrote %s\n", data);
|
|
|
|
/* Close file */
|
|
close(myfile);
|
|
|
|
return 0; // Return success
|
|
}
|
|
else // parent
|
|
{
|
|
/* Wait for child */
|
|
wait(0);
|
|
|
|
/* Read data */
|
|
char data[32] = {0};
|
|
read(myfile, data, sizeof(data));
|
|
printf("Parent received %s from child\n", data);
|
|
|
|
/* Close file */
|
|
close(myfile);
|
|
}
|
|
return 0;
|
|
}
|