I have a program with string literals to specify optional command line arguments. How to process these optional command line arguments in c? -

below syntax command line arguments.

./main [-var1 value] [-var2 value] [-var3 value]

var1,var2 , var3 strings. ex: var1 aaa, var2 bbb, , var3 ccc.

however similar case single characters options, example a, b , c shown below

./main [-a value] [-b value] [-c value]

getopt(argc, argv, "a:b:c:"); can used. there similar way process var1,var2 , var3 program.

getopt historical function processes single letter options, extended 2 companions:

getopt_long: accept single letter options command starting 1 single dash (-a) or multi-letter ones starting 2 (--action)
getopt_long_only: accept multi-letters options starting 1 or 2 dashes (--action or -action)

(following extracts man page)

the signature latter 2 :

int getopt_long(int argc, char * const argv[],        const char *optstring,        const struct option *longopts, int *longindex);

where longopts pointer first element of array of struct option declared in as

struct option {     const char *name;     int         has_arg;     int        *flag;     int         val; };

(the last element of array has filled zeros)

if longindex not null, points variable set index of long option relative longopts.

Abbruzzese