在环境变量中查找一个元素，如果存在的话，将它的值分别打印出来

 1 /*
 2  * Look up a given string in the environment variable,
 3  * print out its values respectively if present.
 4  *
 5  * viechang@gmail.com
 6  */
 7 
 8 #include <stdlib.h>
 9 #include <string.h>
10 #include <stdio.h>
11 
12 #include <iostream>
13 
14 using namespace std;
15 
16 #define ENV_MAX_CHAR    0x0400
17 
18 int
19 main(int argc,
20     char *argv[],
21     char **env)
22 {
23     int cnt = 0;
24 
25     if (argc < 2) {
26         cout << "Usage: a.out <string> " << endl;
27         return EXIT_FAILURE;
28     }
29 
30     for (cnt = 0; env[cnt] != NULL; cnt++) {
31         if (0 == strnicmp(env[cnt], argv[1], 4)) {
32             char *p = (char *)malloc(ENV_MAX_CHAR * sizeof(char));
33             char *pch = NULL;
34 
35             strcpy(p, env[cnt]);
36             cout << "#Splitting string: " << endl;
37             cout << "\"" << p << "\"" << endl;
38             cout << "#into tokens:\n" << endl;
39 
40             pch = strtok(p, "=;");
41             while(pch != NULL) {
42                 cout << pch << endl;
43                 pch = strtok(NULL, "=;");
44             }
45 
46             free(p);
47             break;
48         }
49     }
50     if (env[cnt] == NULL)
51         cout << "Nothing match.";
52 
53     return EXIT_SUCCESS;
54 }