launching a program from a C++ application

Error1312 · 02-24-2004, 06:54 PM

Hello everybody.

I want to make a sort of task manager, but I don't know how to launch a program (for example: OpenOffice) from my own program.

In Windows you would use something like:
system("C:\folder\program.exe");

but I don't know how this works in Linux.

Could somebody help me?

Thanks in advance.

krajzega · 02-24-2004, 07:17 PM

Function exec replaces currently running process into application you want to run:
#include <unistd.h>
exec(const char *path, const char *arguments )

I dont remember whether its function which runs this application as a new process, but you can fork() current process.

itsme86 · 02-24-2004, 07:28 PM

exec() is what you're looking for like krajzega suggested. system() would be a poor choice because it would block your task manager process until the system() function returned.

try something like this in your task manager program:

Code:

// In the task manager process right now

if((pid = fork())
{  // pid is 0 if in the parent process, otherwise it's the new pid
  exec(program, args);
    // Child process is done when exec() returns.
  exit(0);  // Kill the child process. No longer needed.
}

// In the parent process here. Runs in parallel with the child
  printf("PID %d started for program %s\n", pid, program);

chewysplace · 02-24-2004, 09:44 PM

system() works for me in linux. i can get some code later if you'd like.

Error1312 · 02-25-2004, 03:48 AM

Thanks for the answer guys, I haven't tried it yet, but I will do it as soon as possible.

kalleanka · 02-25-2004, 03:51 AM

Library: stdlib.h

Prototype: int system(const char *cmd);

Syntax: system( "cat /etc/hosts");

Notes:
In Unix systems, the command is passed to "/bin/sh -c" for
execution. I do not know what handles the command in DOS systems.

use system in linux.

cjcuk · 02-25-2004, 04:41 AM

Quote:

Originally posted by itsme86

Code:

[ ... ] // Child process is done when exec() returns. exit(0); // Kill the child process. No longer needed. [ ... ]

It is worth noting that exec will only return on error. If it is a success then the old process does not exist for it to return to. Also, if you could still possibly have a forked process running, it is sometimes advisable to use _exit(2) to avoid the spring-cleaning performed by exit(3).

Error1312 · 02-25-2004, 09:18 AM

Thanks for the answers. It works fine now.