getenv 抓不到 $COLUMNS

sprite

1. 
   
2. #include <stdlib.h>
   
3. #include <stdio.h>
   
4. #include <string.h>
   
5. 
   
6. int main(int argc, char *argv[])
   
7. {
   
8.     char *var, *value;
   
9. 
   
10.     if(argc == 1 || argc > 3) {
    
11.         fprintf(stderr,"usage: environ var [value]\n");
    
12.         exit(1);
    
13.     }
    
14.     var = argv[1];
    
15.     value = getenv(var);
    
16.     if(value)
    
17.         printf("Variable %s has value %s\n", var, value);
    
18.     else
    
19.         printf("Variable %s has no value\n", var);
    
20. 
    
21.     exit(0);
    
22. }
    

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[bash@calabash ~]$ ./a.out COLUMNS
Variable COLUMNS has no value
[bash@calabash ~]$ echo $COLUMNS
101



运行环境：fc4

MatthewGong

COLUMNS变量必需是export过的：

1. 
   
2. [matt@gong source]$ ABC=def
   
3. [matt@gong source]$ echo $ABC
   
4. def
   
5. [matt@gong source]$ ./a.out ABC
   
6. Variable ABC has no value
   
7. [matt@gong source]$ export COLUMNS=101
   
8. [matt@gong source]$ ./a.out COLUMNS
   
9. Variable COLUMNS has value 101
   

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sprite

谢谢回复，确实是要export之后才能get。