getopt() / getopt_long()

리눅스에서 옵션으로 -h 나 --help 같이 두가지 옵션으로 주는 것을 처리해주는 api 인데
직접 작성해 본게 아니라 일단.. 이정도만 정리...

struct option declared in <getopt.h> as struct option {     const char *name;     int         has_arg;     int        *flag;     int         val; };  [링크 : http://linux.die.net/man/3/getopt]

extern char *optarg; extern int optind, opterr, optopt;   int getopt_long(int argc, char * const argv[],            const char *optstring,            const struct option *longopts, int *longindex); optstring is a string containing the legitimate option characters. If such a character is followed by a colon, the option requires an argument, so getopt() places a pointer to the following text in the same argv-element, or the text of the following argv-element, in optarg. Two colons mean an option takes an optional arg; if there is text in the current argv-element (i.e., in the same word as the option name itself, for example, "-oarg"), then it is returned in optarg, otherwise optarg is set to zero. This is a GNU extension. If optstring contains W followed by a semicolon, then -W foo is treated as the long option --foo. (The -W option is reserved by POSIX.2 for implementation extensions.) This behavior is a GNU extension, not available with libraries before glibc 2.    [링크 : http://linux.die.net/man/3/getopt_long]

-D 는 옵션을 필요로 하는 녀석이라 :가 붙게 되어 D:가 기재되고
optarg에 해당 문자의 포인터가 들어가게 되어 strdup나 atoi 등을 이용해서 인자를 사용하게 된다.

int main(int argc, char *argv[]) {         struct option long_option[] =         {                 {"help", 0, NULL, 'h'},                 {"device", 1, NULL, 'D'},                 {"rate", 1, NULL, 'r'},                 {"channels", 1, NULL, 'c'},                 {"frequency", 1, NULL, 'f'},                 {"buffer", 1, NULL, 'b'},                 {"period", 1, NULL, 'p'},                 {"method", 1, NULL, 'm'},                 {"format", 1, NULL, 'o'},                 {"verbose", 1, NULL, 'v'},                 {"noresample", 1, NULL, 'n'},                 {"pevent", 1, NULL, 'e'},                 {NULL, 0, NULL, 0},         };          while (1) {                 int c;                 if ((c = getopt_long(argc, argv, "hD:r:c:f:b:p:m:o:vne", long_option, NULL)) < 0)                         break;                 switch (c) {                 case 'h':                         morehelp++;                         break;                 case 'D':                         device = strdup(optarg);                         break;                 case 'r':                         rate = atoi(optarg);                         rate = rate < 4000 ? 4000 : rate;                         rate = rate > 196000 ? 196000 : rate;                         break;                 } [링크 : http://www.alsa-project.org/alsa-doc/alsa-lib/_2test_2pcm_8c-example.html]

[링크 : http://forum.falinux.com/zbxe/?mid=C_LIB&page=3&document_srl=408382] getopt()
[링크 : http://forum.falinux.com/zbxe/index.php?document_srl=519764&mid=C_LIB] getopt_long()
[링크 : http://linux.die.net/man/3/getopt]
[링크 : http://linux.die.net/man/3/getopt_long]