Thread: Starting new program with function

I'm pretty certain there's something in the cboard FAQ - but it may also be about multithreading (just omit the call to fork()).

If you don't want to use fork() you'll need to use system(). The reason is because the exec() family of functions replace the current process image with the new one. So you'd be able to call the second program, but it wouldn't ever get back to the first program. The whole thing would just end when the second program finished. The reason you see fork() before exec() calls is because exec() is called in the child process. That way only the child process image is replaced when you call exec(). Then the parent can just wait for the child process to finish an dthen continue on its way. system() uses fork() internally so you don't have to worry about it.

No it isn't.
[edit]

7.20.4.6 The system function
Synopsis
1

#include <stdlib.h>
int system(const char *string);

Description
2 If string is a null pointer, the system function determines whether the host
environment has a command processor. If string is not a null pointer, the system
function passes the string pointed to by string to that command processor to be
executed in a manner which the implementation shall document; this might then cause the
program calling system to behave in a non-conforming manner or to terminate.
Returns
3 If the argument is a null pointer, the system function returns nonzero only if a
command processor is available. If the argument is not a null pointer, and the system
function does return, it returns an implementation-defined value.

To clarify, the function call itself is not OS specific. It's a standard function.
[/edit]


Quzah.

oh, i thought it is, because in the FAQ of system("pause") is written "A poor-mans method of using system(), OS specific."
Or why else should'nt you use system("pause")? I know it's not that good to use the system-call if the user can define the command string himself...

mfg

[edit]
k, so it depends on the command processor of the running OS, what it makes with it?

The function itself is a standard C function.
The arguments you pass to it are system specific.

If your operating system has a command called 'pause', then doing 'system( "pause" )' will likely invoke it. If it doesn't, then doing 'system( "pause" )' won't. See?

The reason using system is frowned upon is something like this:

Code:

char buf[BUFSIZ] = {0};

puts("Enter something for me to pass off to the OS: ");
fgets( buf, BUFSIZ, stdin );

system( buf );

Not really a good idea.


Quzah.

Because pause is OS specific, not system(). If you don't have a program in your path called "pause" then the system() call will fail. You're just looking at the wrong part of system("pause") as being OS specific.

EDIT: Beaten again by Quzah.

Like this?

Code:

system("\\the\\path\\to\\the\\program\\the_program_name");

system("pointer of location with /, not \\");

You can use either, except for some DOS commands; this will work:

Code:

system("cd \\windows");

but this won't:

Code:

system("cd /windows");