exec functions under unix

This is a discussion on exec functions under unix within the C++ Programming forums, part of the General Programming Boards category; Code: #include <iostream> #include <cstring> #include <ctime> #include <unistd.h> #include <stdlib.h> #include <sys/types.h> #include <stdio.h> #include <poll.h> #include "string2int.h" using ...

  1. #1
    Registered User
    Join Date
    Sep 2004
    Posts
    26

    exec functions under unix

    Code:
    #include <iostream>
    #include <cstring>
    #include <ctime>
    #include <unistd.h>
    #include <stdlib.h>
    #include <sys/types.h>
    #include <stdio.h>
    #include <poll.h>
    #include "string2int.h"
    using namespace std;
    
    
    void parent(int m);
    
    int main()
    {
    	parent(100);
    	return 0;
    }
    
    
    void parent(int m)
    {
    	int pipe1[2];
    	int pipe2[2];
    	pipe(pipe1);
    	pipe(pipe2);
    	char buf[80];
    	const int BSIZE = 100;
    	int pid = fork();
    
    	if(pid < 0)
    		cout<<"ERROR"<<endl;
    	else if(pid == 0)
    	{
    		int b;
    		pollfd my_fds; int poll_ret;
    		my_fds.fd = pipe1[0];
    		my_fds.events = POLLRDNORM;
    		my_fds.revents = POLLRDNORM;
    		buf[0]='a';		
    		do
    		{
    			poll_ret=poll(&my_fds, (nfds_t)1, 10);
    			if(poll_ret>0)
    			{
    				read(pipe1[0],buf,BSIZE);
    				cout<<"parent: ";
    				for(b=0; buf[b]!='#';b++)
    				{
    					if(buf[b] == '*')
    					{
    						cout<<endl;
    						cout<<"parent: ";
    					}
    					else
    						cout<<buf[b];
    				}
    				cout<<endl;
    				write(pipe2[1],"RESPONSE#",9);
    			}
    		}while(buf[0] != 'b');	
    	}
    	
    	else
    	{
    		int numMsgs=m;  const int BSIZE2 =100;
    		int msgCount=1; int n;
    		string pLinStr;
    		string pMsgStr;
    		int pRanLines;
    		int lineTot=0;
    		char response[80];
    		char pMsgLine[80];
    		pollfd my_fds2; int poll_ret2;
    		my_fds2.fd = pipe2[0];
    		my_fds2.events = POLLRDNORM;
    		my_fds2.revents = POLLRDNORM;
    		int x;
    		int y;
    		int z;
    		int a;
    		srand(time(0));
    		while(msgCount < 101)
    		{
    			pRanLines = (1+ rand() %5);
    
    			if(msgCount == 100)
    				write(pipe1[1],"bye#",4); 
    			else
    			{
    				y=0;
    				for(x=0; x<pRanLines; x++)
    				{
    					pMsgLine[y] = 'm';
    					y++;
    					pMsgStr = BasicTypeToStr(msgCount);
    					for(z=0; z<pMsgStr.size(); z++)
    					{
    						pMsgLine[y]=pMsgStr[z];
    						y++;
    					}	
    					pMsgLine[y]=' ';
    					y++;
    					pMsgLine[y]='l';
    					y++;
    					pMsgLine[y]='i';
    					y++;
    					pMsgLine[y]='n';
    					y++;
    					pMsgLine[y]='e';
    					y++;
    					pMsgLine[y]=' ';
    					y++;
    					lineTot++;
    					pLinStr=BasicTypeToStr(lineTot);
    					for(z=0; z<pLinStr.size(); z++)
    					{
    						pMsgLine[y]=pLinStr[z];
    						y++;
    					}
    					pMsgLine[y]='*';
    					if(x == pRanLines-1)
    						pMsgLine[y]='#';
    					y++;
    
    				}
    				write(pipe1[1], pMsgLine, y);
    				
    			
    				do
    				{
    					poll_ret2=poll(&my_fds2, (nfds_t)1, 10);
    					if(poll_ret2>0)
    					{
    						read(pipe2[0],response,BSIZE2);
    						for(a=0;response[a]!='#';a++)
    							cout<<response[a];
    						cout<<endl;
    					}
    	
    				}while(poll_ret2 <= 0);			
    			}
    			msgCount++;
    		}
    	}
    
    }
    the code within else if(pid == 0) statement needs to be executed in that is another image, and I need to use one of the exec() fucntions, how could i make it so that the code executes in a different file and pass the pipes to the code so that messages can be transfered?

  2. #2
    Registered User
    Join Date
    Mar 2002
    Posts
    1,595
    you can use (almost) any number of files you want in any given program by associating them with a "stream". The "stream" you use will differ based on whether you use C or C++ syntax. Details on using streams to access files is available in the FAQ section---I believe.

    The FAQ section also review several ways to run different programs from within your current program.

    Good luck.

  3. #3
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    Sep 2004
    Posts
    26
    according to the specs i have to use one of the exec functions to create a new child process image.....

  4. #4
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    Join Date
    Mar 2002
    Posts
    1,595
    maybe this will help, seemed semi-relevant from my point of view, not being familiar with exec(), anyway.

    http://www.opengroup.org/onlinepubs/...ions/exec.html
    This sounds like the information you need to pass to one of the exec() functions listed comes from the command line. An example is provided.

    Good luck.

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