When running the code below I get an incorrect output. I am fairly sure I am doing something wrong with the execvp call as I have tried changing everything and only this seems to be responsible. As far as I know the parameters for execvp should be the filename and the array which I pass using execvp(argv[0], argv). Replacing these parameters with things such argv[1] seems to change the output which is why I think I am doing something wrong here.
a.out file -> lab1 (g++ lab1.cpp -o lab1)
folder -> lab1
.cpp file -> lab1.cpp
current output:
steve@fish lab1]$ lab1 ls -l
lab1 ls -l Parent process id is: 1747646
lab1 ls -l Child process id is: 1747647
[vnath@storm lab1]$ lab1: cannot access 'ls': No such file or directory
What output should be:
steve@fish lab1]$ lab1 ls -l
lab1 ls -l Child process pid is 7302
total 30
-r-xr-xr-x 1 steve staff 3567 Aug 17 07:45 lab1
-rwxr--r-- 1 steve staff 547 Aug 17 08:00 lab1.cpp
-rw-r--r-- 1 steve staff 11291 Aug 17 08:15 lab1.html
-rw-r--r-- 1 steve staff 621 Aug 17 09:59 linux.txt
lab1 ls -l Parent process pid is 7301
code:
#include <iostream>
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/wait.h>
using namespace std;
int main(int argc, char* argv[])
{
int ppid = 0;
int cpid = 0;
pid_t pid = fork();
if(pid == -1) // error handling
{
perror("fork");
return 1; // added
}
if(pid == 0) // child process
{
//cpid = pid;
cpid = getpid();
for(int i = 0; i < argc; i++)
cout << argv[i] << " ";
cout << "Child process id is: " << cpid << endl;
if(execvp(argv[1], argv) < 0)
{
perror("exec");
return 1;
}
}
if(pid > 0) // parent process
{
ppid = getpid();
for(int i = 0; i < argc; i++)
cout << argv[i] << " ";
cout << "Parent process id is: " << ppid << endl;
}
return 0;
}
For anyone curious turns out execvp(argv[1], &argv[1]) is the key to get it all working.