pipe()/fork()/execl() functions do not return output of external program

engintozal (2)
Hello, I am writing a program which calls an external program and obtains its output(standard output). I implemented this functionality as a method. When I called the method for the first time it successfully obtains the output, however, when I called multiple times in the same main() it does not obtain the output of the external program except the first call (i.e. I cant read-in the output of the secınd call and the following ones) Could anyone please help me. engin Below is the main structure of the method: ...::ally(){ allyString.clear();//to collect the output of external program pid_t pid; int commpipe[2]; int status; if(pipe(commpipe)==-1){ cout<<"Error in opening pipe"<<endl; exit(1); } pid=fork(); if(pid==-1){ cout<<"Error in forking"<<endl; exit(1); } if(pid>0){//parent process close(commpipe[1]); dup2(commpipe[0],0);//replace stdin with read side of pipe wait(&status);//wait for the child to finish while(!cin.eof()){ char c=cin.get(); allyString.push_back(c); } close(commpipe[0]); }else{//child process close(commpipe[0]); dup2(commpipe[1],1);//replace stdout with write side of pipe if(execl("/src/local/bin/ally", "ally","154.54.20.26", "154.54.20.26",(char *)0)==-1){//the external program cout<<"Error in executing the external ally program "<<endl; exit(1); } cout<<"Finished Child process"; close(commpipe[1]); } }