I wanted to #define some macros based on whether particular directory is present in Linux, I can't use any fopen/directory/stat API's here since they are exposed during compilation phase
Example,
Need to set ---->Someway to check directory existing using C macro, i.e before compilation phase #define RANDOM 100 #else #define RANDOM 200
Need help here.
You can define a macro from the command line using the -D preprocessor option, in your case:
gcc -o demo demo.c -DRANDOM=$(test -d /path/to/some/dir && echo 100 || echo 200)
You simply read RANDOM from your program:
#include <stdio.h>
int main(void)
{
printf("%d\n", RANDOM);
}
You can't do this as the preprocessor textually replaces one value with another (more precisely it replaces tokens). It is done before the actual C code compilation.
You need to have variable RANDOM (not macro definition) and assign it with the value runtime.
int RANDOM = 0;
if(directory_exists(directory))
{
RANDOM = 200
}
else
{
RANDOM = 500
}
and use it later in your code.
