Hi,
I'd like to know if I can call a program from a program and receive result.
I've this complied C program (Called):
Can I call this program from another C program and receive "i" ?Code:/* omissis header */ int main() { int i = 0; i = rand(); return i; }
My pseudo-code would be:
Does the "return" instruction pass data also through compiled programs?Code:/* omissis */ int dest = 0; dest = call Called program; /* omissis */
How to do it? How to call external programs?
Thanks
You can't do this portably.
On unix, system() (which is a standard function) will return the termination status of whatever you're running. But remember that you only get 8 bits for the return value, so you can only return values 0-255.
Again assuming unix, you could have one program print out a number and then the other program use popen() to grab the output and parse it. This is somewhat analogous to using `` or $() in the Bourne shell; it just takes a bit more work to do.
I'm not familiar with other platforms so I can't comment on them.
ShellExecuteEx and GetExitCodeProcess can do this for Windows.
Originally Posted by Adak
popen() also works on Windows.
The 'best' way on Windows I'd say is, CreateProcess() with inherited pipes (stdout, stdin or stderr).
That means you can send more than just 1 thing, or just a number.
system() should be sufficient for getting the error/return code of the process.
It is too clear and so it is hard to see.
A dunce once searched for fire with a lighted lantern.
Had he known what fire was,
He could have cooked his rice much sooner.
And where is the result stored?
Thanks (sorry, I'm new with C)
System returns what is returned by the program it executes.
System returns an int.
It is too clear and so it is hard to see.
A dunce once searched for fire with a lighted lantern.
Had he known what fire was,
He could have cooked his rice much sooner.
But, I mean, if I want to use this result, where do I find it. Have I to use something like this:
?Code:int take = 0; take = system("extern.exe");
In the example you gave, you'd find the result in the take variable. So whatever value main() returned in extern.exe is what take should equal.
Except the case when was error starting the external program. In any case - you should read the description of system function in C-reference, especially - the return value.
All problems in computer science can be solved by another level of indirection,
except for the problem of too many layers of indirection.
– David J. Wheeler
