C++ System command outputs 0 at end

Question

So I am writing a C++ program that runs a command within the program. Whenever I do run the command though, it outputs a 0 at the end of whatever its supposed to output. Example:

The random int I was thinking of was 130

Where it is only supposed to output The random int I was thinking of was 13 but it still outputs the 0 at the end. Here is my code to run the command:

printf("Running file: %s\n", fileName);
if(!exists(fileName))
{
    printf("That file does not exist.\n");
    return;
}
char buffer [7+strlen(fileName)];
int n;
n = sprintf(buffer, "php -f %s", fileName);
cout << system(buffer) << endl;

I dont think it has anything to do with the php command, because whenever I type into my terminal, php -f <filenamehere> it comes out with the The random int I was thinking of was 13 output. I cannot think of anything else.

`system()` returns 0 to indicate success (and non-zero to indicate failure). You print this 0. — Igor Tandetnik, Feb 21 '16 at 17:54
You don't send the return value of `system()` to `cout`, of course. — Igor Tandetnik, Feb 21 '16 at 17:58
Another problem: wrong size of the buffer, there is no space for terminating 0, which means you are going out of bounds. — Revolver_Ocelot, Feb 21 '16 at 18:01

Mats Petersson · Accepted Answer · 2016-02-21T18:13:05.757

The system function returns the "result" of the execution, which is 0 for success, other values for various types of failure (including the result of the executable itself, if applicable).

You are printing that value using cout, which is why it's printing 0 - which is why it's printing 0.

You probably want to do something like this:

int result = system(...);
if (result != 0) 
{
   cout << "system returned " << result << " which means it failed..." << endl;
}

Note that the output of whatever you run using system will go to stdout, it is not returned to the application itself, it is just printed to the console [or wherever stdout is going].

score 0 · Answer 2 · edited May 23 '17 at 12:14

0

system command return only the execution status.

To capture and print the output, see the options in this link

How to execute a command and get output of command within C++ using POSIX?

edited May 23 '17 at 12:14

Community

1
1

answered Feb 21 '16 at 18:36

Sam Daniel

1,800
12
22

C++ System command outputs 0 at end

2 Answers2