Parameter to system() func?

Question

I want to send an integer as a parameter to the system() function in C, but I haven't been able to.

I'd like to do this because I have some jpg files which are regularly named as 1.jpg , 2.jpg ... 17.jpg ... ect. The program would assign a randomly chosen value to an integer variable, and open the image file with the same name as the randomly chosen integer by using the system() function.

What I envision:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

main()
{
    srand(time(NULL));
    i=rand()%30+1; // for example i=17
    system("eog %d.jpg &",i);  //and i want to open 17.jpg here with eog
}   

I know there are too many arguments to the system() function above; I just wanted to give an example of what I wanted.

Is there a way to do this, and if not, how else could I go about doing what I described above?

Answer 1

You need to convert the integer into a string argument:

int runSystem(const char *fmt, ...)
{
    char buffer[4096];
    va_list va;
    va_start(va, fmt);
    vsnprintf(buffer, sizeof(buffer), fmt, va);
    va_end(va);
    return system(buffer);
}

main()
{
    srand(time(NULL));

    i=1+rand()%30; // for example i=17

    runSystem("eog %d.jpg &",i);  //and i want to open 17.jpg here with eog

}   

Answer 2

Use snprintf to build your string and pass that to system.

char cmd[LEN];
snprintf(cmd, sizeof(cmd), "eog %d.jpg &", i);
system(cmd);