c関数でshellコマンドを実行する

 c     shell             

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

int main(void)
{
    int ret = -1;
    FILE* pf;
    /* Can not get the output of the cmd */
    ret = system("ls /dev/loop* | wc -l");

    printf("ret = %d
", ret);
    
    /* This mothed can get the output of the cmd */
    pf  = popen("ls /dev/loop* | wc -l", "r");

    fscanf(pf, "%d", &ret);
    printf("ret = %d
", ret);

    pclose(pf);
    return 0;
}