Get environment variables in C on linux
The unknown main() parameter
The main can in fact take a parameter,
char* env[] which is an array containing all environment variables and ending with a NULL string.
A small minimalist example of its use:
#include <stdio.h>
int main(int argc, char* argv[], char* env[]){
int i;
for(i=0;env[i]!=NULL;i++)
printf("%s\n",env[i]);
return 0;
}The getenv fonction
Getenv which the prototype is the following 'char* getenv (const char* name)' is part of 'stdlib.h'.
It allows you to retrieve an environment variable.
#include <stdio.h>
#include <stdlib.h>
int main(int argc,char* argv[]) {
char* user=getenv("USER");
if(user!=NULL)
printf("USER='%s'\n",user);
return 0;
}
Do not hesitate to consult the getenv man page for more information.
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