problem with fork()
- by john
I'm writing a shell which forks, with the parent reading the input and the child process parsing and executing it with execvp.
pseudocode of main method:
do{
pid = fork();
print pid;
if (p<0) { error; exit; }
if (p>0) { wait for child to finish; read input; }
else { call function to parse input; exit; }
}while condition
return;
what happens is that i never seem to enter the child process (pid printed is always positive, i never enter the else). however, if i don't call the parse function and just have else exit, i do correctly enter parent and child alternatingly.
full code:
int main(int argc, char *argv[]){
char input[500];
pid_t p;
int firstrun = 1;
do{
p = fork();
printf("PID: %d", p);
if (p < 0) {printf("Error forking"); exit(-1);}
if (p > 0){
wait(NULL);
firstrun = 0;
printf("\n> ");
bzero(input, 500);
fflush(stdout);
read(0, input, 499);
input[strlen(input)-1] = '\0';
}
else exit(0);
else { if (parse(input) != 0 && firstrun != 1) { printf("Error parsing"); exit(-1); } exit(0); }
}while(strcmp(input, "exit") != 0);
return 0;
}
