c - Write the integer 0 to file, read the file, increment integer to 10, and arrange it through the child and parent process -
this has been done before, trouble code not incrementing, doing else fine. want have output of file reads integer loop going to. instead, gets stuck @ 0. need help. writing in c. here code:
assignment9.c:
#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/stat.h> #include "tellwait.h" void err_sys(const char* message); int main(void){ file *filepoint; int* 0 = 0; int val; char* buffer[180]; pid_t pid; filepoint = fopen("testfile.txt", "w+"); fprintf(filepoint, "%d", zero); tell_wait(); if((pid = fork()) < 0) { err_sys("fork error"); } else if (pid == 0) //child { int i; for(i = 0; < 10; i++){ wait_parent(); filepoint = fopen("testfile.txt", "w+"); fread(buffer, sizeof(zero), 1, filepoint); // increment val = atoi(buffer[0]); val++; // use fprintf write file //printf("current amount: %d, child process\n", zero); printf("%d\n", val); fprintf(filepoint, "%d", val); tell_parent(pid); } } else { //parent int i; for(i = 0; < 10; i++){ filepoint = fopen("testfile.txt", "w+"); fread(buffer, sizeof(zero), 1, filepoint); // increment val = atoi(buffer[0]); val++; // use fprintf write file //printf("current amount: %d, parent process\n", zero); printf("%d\n", val); fprintf(filepoint, "%d", val); tell_child(pid); wait_child(); } } return exit_success; } void err_sys(const char* message) { printf("%s\n", message); exit(0); } tellwait.h:
#ifndef _tell_wait_h #define _tell_wait_h void tell_wait(void); /* parent/child {sec race_conditions} */ void tell_parent(pid_t); void tell_child(pid_t); void wait_parent(void); void wait_child(void); #endif tellwait.c:
#include <stdlib.h> #include <signal.h> void err_sys (const char* message); static volatile sig_atomic_t sigflag; /* set nonzero sig handler */ static sigset_t newmask, oldmask, zeromask; static void sig_usr(int signo) /* 1 signal handler sigusr1 , sigusr2 */ { sigflag = 1; } void tell_wait(void) { if (signal(sigusr1, sig_usr) == sig_err) err_sys("signal(sigusr1) error"); if (signal(sigusr2, sig_usr) == sig_err) err_sys("signal(sigusr2) error"); sigemptyset(&zeromask); sigemptyset(&newmask); sigaddset(&newmask, sigusr1); sigaddset(&newmask, sigusr2); /* block sigusr1 , sigusr2, , save current signal mask */ if (sigprocmask(sig_block, &newmask, &oldmask) < 0) err_sys("sig_block error"); } void tell_parent(pid_t pid) { kill(pid, sigusr2); /* tell parent we're done */ } void wait_parent(void) { while (sigflag == 0) sigsuspend(&zeromask); /* , wait parent */ sigflag = 0; /* reset signal mask original value */ if (sigprocmask(sig_setmask, &oldmask, null) < 0) err_sys("sig_setmask error"); } void tell_child(pid_t pid) { kill(pid, sigusr1); /* tell child we're done */ } void wait_child(void) { while (sigflag == 0) sigsuspend(&zeromask); /* , wait child */ sigflag = 0; /* reset signal mask original value */ if (sigprocmask(sig_setmask, &oldmask, null) < 0) err_sys("sig_setmask error"); } the file output testfile.txt 10, while test console output attempting is:
1 2 3 4 5 6 7 8 9 10 may please me?