environhostname.c

从environ获得HostName

#include <stdio.h>
#include <string.h>

int main(int argc, char **argv)
//int main(int argc, char *argv[])
{
  extern char **environ;
  char **p;

  int i = 0;

  char token[128];
  char value[1024];

  for (p = environ; *p != NULL; p++)
  {
    i++;
    fprintf(stdout, "%4d:%s\n", i, *p);

    // char *strchr(const char *s, int c);
    char *pos;

    // Upon completion, strchr() shall return a pointer to the byte, or a null pointer  if  the  byte  was  not found.
    pos = strchr(*p, '=');

    //fprintf(stdout, "debug: pos = %c\n", *pos);

    if (pos == NULL)
    {
      fprintf(stderr, "cannot find token.\n");
      break;
    }

    memset(token, 0, sizeof(token));
    memcpy(token, *p, pos - *p);
    //token[pos-*p] = '\0';

    //fprintf(stdout, "debug: token = %s\n", token);

    memset(value, 0, sizeof(value));
    memcpy(value, pos + 1, strlen(*p) - (pos - *p + 1));

    fprintf(stdout, "debug: value = %s\n", value);

    if (!strcmp(token, "HOSTNAME"))
    {
      fprintf(stdout, "found it! HOSTNAME=%s\n", value);
    }
  }

  return 0;
}