/* test1.c */
#include <stdio.h>
#include <stdlib.h>
int main()
{
int m = 11;
system("./test2 m");
return 0;
}
The above program prints 0, whereas I expect it to print 11.
/* test2.c */
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
int m = atoi(argv[1]);
printf("%d\n", m);
return 0;
}
Can someone provide an explanation? Also what would be the right way in order to print the desired 11?
You are passing the character m to the command line, not its value.
The system() function just takes a string as its argument. It doesn't know that you have a variable named m and that it should substitute that variable in the string (Which would not be possible in C anyways with such a syntax.)
That means you are executing your second program like this:
./test2 m
Your 2 program does atoi(argv[1]); , which will then be the same as atoi("m"); , which makes atoi() return 0.
You need to build up the string you want system() to execute
int main(int argc, char *argv[])
{
char command[128];
int m = 11;
sprintf(command , "./test2 %d", m);
system(command);
return 0;
}
C does not expand variables in string constants like perl so m in your command string is a string constant.
What you need to do is print the value of mto the command string:
/* test1.c */
#include <stdio.h>
#include <stdlib.h>
int main()
{
int m = 11;
char buf[100];
sprintf(buf, "./test2 %d", m);
system(buf);
return 0;
}
int before m ;)