Question

I am creating a simple Unix shell in C. I use the fork() to clone the process and exec to execute a new one. It works fine when you are inputting data for the first time in the shell. But when it comes the second iteration fork returns -1.

e.g

…>ls -l /

/results here/

…>ls -l /

forking failed

here is a part of the code:

int execute(char path[80],char *args[]){
pid_t pid;
if((pid=fork())<0){
 printf("forking failed"); // The forking failed due to Cannot allocate memory error
 exit(0);
}else if(pid==0){
 execv(path,args);
}else{
 wait(NULL);
}
return 0
}

where path is “bin/ls” and args “ls”,NULL

the main is looks like

int main(){
 while(1){
 //read from keyboard
 //find the program path
 //fill args
 execute(path,args);
 }
}

Answer 1

Change your first if branch to this:

if((pid=fork())<0){
 perror("forking failed");
 exit(0);
}

This will tell you what went wrong.