i trying run program following actions:
- fork child process launch compiled c program- draw.out
- the parent process waits user input keyboard
- input passes draw.out program via pipe
- draw.out reads pipe , uses input
here 2 programs, draw.out works fine (tetris game) isn't getting input pipe, mistake?
file 1:
#include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <signal.h> #include <sys/wait.h> #include <errno.h> #include <stdlib.h> #include <curses.h> #include <string.h> int main(void) { int fd[2], childpid; //pid_t childpid; char input = 'o'; char readbuffer[80]; pipe(fd); if ((childpid = fork()) == -1) { perror("fork"); exit(1); } if (childpid == 0) { close(0); dup(fd[0]); execl("draw.out", null); } else { close(fd[0]); while (input != 'q') { input = getch(); if (input == 'a' || input == 's' || input == 'd' || input == 'w' || input == 'q') { write(fd[1], &input, 1); kill(getpid() + 1, sigusr2); } } exit(0); } return 1; } file 2:
#include <signal.h> #include <stdio.h> #include <sys/types.h> #include <unistd.h> #include <string.h> #include <stdlib.h> void print_screen(int a, int b, int c, int t, int flat); void my_handler(int signum); int = 9, b = 10, c = 11, t = 0, flat = 1; int newfd = 0; int main(void) { if (signal(sigusr2, my_handler) == sig_err) { printf("pærent: unable create handler sigusr2\n"); } while (t < 20) { system("clear"); print_screen(a, b, c, t, flat); sleep(1); t++; } } void my_handler(int signum) { if (signum == sigusr2) { printf("signal arrived"); char input; fgets(&input, sizeof(input), stdin); switch (input) { case 'a': if (a > 1) { a--; b--; c--; } break; case 's': t++; break; case 'd': if (c < 18) { a--; b--; c--; } case 'w': if (flat == 1) { flat = 0; } else { if (b<18 && b>1) { flat = 1; } } break; case 'q': exit(0); } } } void print_screen(int a, int b, int c, int t, int flat) { char str[420] = "\n"; int i, j; (i = 0; < 20; i++) { (j = 0; j < 20; j++) { if (i != 19 && !(j>0 && j < 19)) { strcat(str, "*"); } else if (i == 19) { strcat(str, "*"); } else { if (flat == 1 && == t && (j == || j == b || j == c)) { strcat(str, "-"); } else if (flat == 0 && j == b && (i == t || == t - 1 || == t + 1)) { strcat(str, "-"); } else { strcat(str, " "); } } } strcat(str, "\n"); } puts(str); }
first: cannot read 1 byte fgets. man fgets:
fgets() reads in @ 1 less size characters stream
as sizeof(input) 1 "one less size" 0. fets read nothing. change fgetc example.
second: kill(getpid() + 1, sigusr2); statement wrong, because assume child have pid of process + 1. wrong assumption, , there no need of such construction, since have childpid variable correctly set.
third: not initalizing ncurses initscr(), getch() won't work. reconfigure terminal add "\n\r" @ end of each line instead of "\n". , don't forget de-initialize ncruses calling endwin() before exiting.
fourth: doing more complicated getting/setting simple variables in signal handlers bad idea. should poll input in main loop using select function, this:
struct timeval time; time.tv_sec = 0; time.tv_usec = 0; fd_set set; fd_zero(&set); fd_set(0, &set); if (select(1, &set, null, null, &time) > 0) { handle_input(); } fifth: you're missing break statement in case, both d , a keys decrementing variables, while d should incrementing guess.
here code works:
#include <signal.h> #include <stdio.h> #include <sys/types.h> #include <unistd.h> #include <string.h> #include <stdlib.h> void print_screen(int a, int b, int c, int t, int flat); void handle_input(void); int = 9, b = 10, c = 11, t = 0, flat = 1; int newfd = 0; int main(void) { int t = 0; while (t < 20) { system("clear"); print_screen(a, b, c, t, flat); sleep(1); struct timeval time; time.tv_sec = 0; time.tv_usec = 0; fd_set set; fd_zero(&set); fd_set(0, &set); if (select(1, &set, null, null, &time) > 0) { handle_input(); } t++; } return 0; } void handle_input() { char input; input = fgetc(stdin); switch (input) { case 'a': printf("a\n"); if (a > 1) { a--; b--; c--; } break; case 's': t++; break; case 'd': if (c < 18) { a++; b++; c++; } break; case 'w': if (flat == 1) { flat = 0; } else { if (b<18 && b>1) { flat = 1; } } break; case 'q': exit(0); } } void print_screen(int a, int b, int c, int t, int flat) { char str[4200] = "\n"; int i, j; (i = 0; < 20; i++) { (j = 0; j < 20; j++) { if (i != 19 && !(j>0 && j < 19)) { strcat(str, "*"); } else if (i == 19) { strcat(str, "*"); } else { if (flat == 1 && == t && (j == || j == b || j == c)) { strcat(str, "-"); } else if (flat == 0 && j == b && (i == t || == t - 1 || == t + 1)) { strcat(str, "-"); } else { strcat(str, " "); } } } strcat(str, "\n\r"); } puts(str); } second file:
#include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <signal.h> #include <sys/wait.h> #include <errno.h> #include <stdlib.h> #include <string.h> #include <ncurses.h> int main(void) { int fd[2]; pid_t childpid; char input = 'o'; pipe(fd); if ((childpid = fork()) == -1) { perror("fork"); exit(1); } if (childpid == 0) { close(0); dup(fd[0]); execl("draw.out", "draw.out", null); } else { close(fd[0]); initscr(); while (input != 'q') { read(0, &input, 1); if (input == 'a' || input == 's' || input == 'd' || input == 'w' || input == 'q') { write(fd[1], &input, 1); } } endwin(); exit(0); } return 0; } 
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