[C Language] getopt parameter optind and its main (INT argc, char ** argv) Parameter Interpretation

Getopt is used to parse command line option parameters.
# Include <unistd. h>

Extern char * optarg; // parameter pointer of the option
Extern int optind, // when getopt is called next time, check the option again from the position where optind is stored.
Extern int opterr, // when opterr = 0, getopt does not output an error message to stderr.
Extern int optopt; // when the command line option character is not included in optstring or the option lacks necessary parameters, this option is stored in optopt, and getopt returns '? '

 

 1 #include <stdio.h>   2 #include <unistd.h>   3 #include <stdlib.h> 4  5 #ifdef RDP2 6 #define VNCOPT "V:Q" 7 #else 8 #define VNCOPT "V:" 9 #endif10  11 int main(int argc, char **argv)  12 {  13         int ch, i;  14         opterr = 0;15 16         while ((ch = getopt(argc,argv, VNCOPT ":a:bcde::f"))!=-1)  17         {  18             printf("optind:%d，opterr：%d\n", optind, opterr);  19                 switch(ch)  20                 {         21                         case ‘V‘:22                                 printf("option V:‘%s‘\n",optarg);23                                 break; 24                         case ‘a‘: 25                                 i = strtol(optarg, NULL, 16);26                                 printf("i = %x\n", i); 27                                 printf("option a:‘%s‘\n",optarg);  28                                 break;  29                         case ‘b‘:  30                                 printf("option b :b\n");  31                                 break; 32                         case ‘e‘:33                                 printf("option e:‘%s‘\n",optarg);34                                 break; 35                         default:  36                                 printf("other option :%c\n",ch);  37                 }  38         }39         for(int i = 0; i < argc; i++)40             printf("argv[%d] = [%s]\n", i, argv[i]);41         printf("argc = [%d]\n", argc); 42         printf("optopt +%c\n",optopt);  43 44     return 1;45 }

Execution result:

$ ./getopt -a 123 -bcd -e 456i = 123option a:‘123‘optind:3，opterr：0option b :boptind:3，opterr：0other option :coptind:3，opterr：0other option :doptind:4，opterr：0option e:‘456‘optind:6，opterr：0argv[0] = [./getopt]argv[1] = [-a]argv[2] = [123]argv[3] = [-bcd]argv[4] = [-e]argv[5] = [456]argc = [6]optopt +eoptind = 6

 

Argv array stores command line strings (including./getopt executable programs)

Argc command line string count (./getopt-A 123-BCD-e 456) 6

When optind calls getopt next time, it re-checks the option from the position where optind is stored. Start from 0

(Corresponding to the following position)

./Getopt-A 123-BCD-e 456

0 1 2 3 4 5 6