popt - basic example

About

A basic example of using popt.

In the manpages for popt is a small example which is taken from a program called "robin". However, without having a familiarity with the program or understanding what the options are for, I found it hard to see from the example how to use the popt library effectively.

A Clean Example

The following alternative example constructs a command-line program, popt_basic, which takes three artificial options, optiona, optionb, and optionc, all of which take integer arguments, and two "flag" options, flag1 and flag2, each of which may either be specified or left off of the commandline. The example program uses popt to process the commandline. Finally, any remaining arguments after the options are handled during the "[ARG...]" portion of the commandline.

Example calls

popt_basic -?

Show the help text which is generated from popt.

popt_basic

Called without any arguments, the program shows the basic usage by calling poptPrintUsage.

popt_basic -a123 -b 456 -c=789

Use short option names a, b, and c to set the options and give example integer arguments. Notice the variety of ways which integer arguments may be supplied to an option.

popt_basic -fg --optiona=123 --optionb=456 --optionc=789

Use short option names for flags f and g, and use long option names for options a, b, and c.

popt_basic ONE TWO THREE

Give three arguments for the "[ARG...]" portion of the commandline.

popt_basic -- -1 -2 -3

Give three arguments for the "[ARG...]" portion which may include a minus sign in the beginning.

Code Listing

 #include <stdio.h>  
 #include <stdlib.h>  
 #include <popt.h>  
   
 // Examples commandlines:  
 // popt_basic -a 123 -b 456 -c 789   
 // popt_basic --optiona=123 --optionb=456 --optionc=789  
 int main(int argc, char *argv[])  
 {  
     // values for optiona, optionb, optionc, flag1, flag2  
     // These values will be updated by popt  
     int optiona=-1, optionb=-1, optionc=-1;   
     int flag1=0, flag2=0;  
       
     // options a, b, c take integer arguments  
     // options f and g take no arguments  
     poptContext pc;  
     struct poptOption po[] = {  
         {"optiona", 'a', POPT_ARG_INT, &optiona, 11001, "descrip1", "argDescrip1"},  
         {"optionb", 'b', POPT_ARG_INT, &optionb, 11002, "descrip2", "argDescrip2"},  
         {"optionc", 'c', POPT_ARG_INT, &optionc, 11003, "descrip3", "argDescrip3"},  
         {"flag1", 'f', POPT_ARG_NONE, &flag1, 11004, "descrip4", "argDescrip4"},  
         {"flag2", 'g', POPT_ARG_NONE, &flag2, 11005, "descrip5", "argDescrip5"},  
         POPT_AUTOHELP  
         {NULL}  
     };  
       
     // pc is the context for all popt-related functions  
     pc = poptGetContext(NULL, argc, (const char **)argv, po, 0);  
     poptSetOtherOptionHelp(pc, "[ARG...]");      
     if (argc < 2) {  
         poptPrintUsage(pc, stderr, 0);  
         exit(1);  
     }  
       
     // process options and handle each val returned  
     int val;  
     while ((val = poptGetNextOpt(pc)) >= 0) {  
         printf("poptGetNextOpt returned val %d\n", val);  
     }  
       
     // poptGetNextOpt returns -1 when the final argument has been parsed  
     // otherwise an error occured  
     if (val != -1) {  
         // handle error  
         switch(val) {  
         case POPT_ERROR_NOARG:   
             printf("Argument missing for an option\n");  
             exit(1);  
         case POPT_ERROR_BADOPT:   
             printf("Option's argument could not be parsed\n");  
             exit(1);  
         case POPT_ERROR_BADNUMBER:  
         case POPT_ERROR_OVERFLOW:   
             printf("Option could not be converted to number\n");  
             exit(1);  
         default:  
             printf("Unknown error in option processing\n");  
             exit(1);  
         }  
     }  
       
     // Handle ARG... part of commandline  
     while (poptPeekArg(pc) != NULL) {  
         char *arg = (char*)poptGetArg(pc);  
         printf("poptGetArg returned arg: \"%s\"\n", arg);  
     }  
       
     // Done. Print final result.  
     printf("--- end of popt_basic ---\n");  
     printf("final value of optiona: %d\n", optiona);  
     printf("final value of optionb: %d\n", optionb);  
     printf("final value of optionc: %d\n", optionc);  
     printf("final value of flag1: %d\n", flag1);  
     printf("final value of flag2: %d\n", flag2);  
     return 0;  
 }  
   

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