91 lines
2.4 KiB
C
91 lines
2.4 KiB
C
#include <unistd.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/wait.h>
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#define LOOPS_PER_CHILD 2000
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#define CHILDS 30
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#define PIPE_READ 0
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#define PIPE_WRITE 1
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int main() {
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int pipes[CHILDS][2];
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pid_t childToPipes[CHILDS];
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for (int child = 0; child < CHILDS; child++) {
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if (pipe(pipes[child]) == -1) {
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fprintf(stderr, "Error creating pipe for child %d: %s\n", child, strerror(errno));
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return 2;
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}
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pid_t pid = fork();
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if (pid == -1) {
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fprintf(stderr, "Error forking: %s\n", strerror(errno));
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return 1;
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} else if (pid == 0) {
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// I AM FORK!
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pid_t childPid = getpid();
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// close read of pipe
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close(pipes[child][PIPE_READ]);
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int start = child * LOOPS_PER_CHILD;
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long sum = 0;
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for (int i = start; i < start + LOOPS_PER_CHILD; i++) {
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fprintf(stdout, "%d: %d\n", childPid, i);
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fflush(stdout);
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sum += i;
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}
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printf("Fork %d finished counting from %d. Sum is %d\n", childPid, start, sum);
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if (write(pipes[child][PIPE_WRITE], &sum, sizeof(sum)) == -1) {
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fprintf(stderr, "Error writing pipe for child %d: %s\n", child, strerror(errno));
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return 4;
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}
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close(pipes[child][PIPE_WRITE]);
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return 0;
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} else {
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// close write of pipe
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close(pipes[child][PIPE_WRITE]);
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childToPipes[child] = pid;
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printf("Fork %d successfull\n", pid);
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}
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}
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// wait for all childs to terminate
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pid_t childPid;
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long overallSum = 0;
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while ((childPid = wait(NULL)) != -1) {
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printf("Child %d terminated\n", childPid);
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long sum = -1;
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for (int child = 0; child < CHILDS && sum == -1; child++) {
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if (childToPipes[child] == childPid) {
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read(pipes[child][PIPE_READ], &sum, sizeof(sum));
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close(pipes[child][PIPE_READ]);
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}
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}
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if (sum != -1) {
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overallSum += sum;
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} else {
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fprintf(stderr, "Error reading from pipe\n");
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return 3;
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}
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}
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printf("Overall Sum: %d\n", overallSum);
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return 0;
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fork();
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fork();
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fork();
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printf("Hello World\n");
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}
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