getopt()

getopt()

参数、变量说明

#include <unistd.h>
int getopt(int argc, char * const argv[],
		  const char *optstring);

extern char *optarg;
extern int optind, opterr, optopt;

argc, argv: 跟 main() 一直

optstring: 接受的选项即选项类别（见下文）。

optarg: 如果选项带参数，则 optarg 指向参数字符串，如 -axxx, 如果 a 是可以接受参数的选项（见下文），则 optarg 指向字符串 "xxx".

optind: option index. The variable optind is the index of the next element to be processed in argv. The system initializes this value to 1. The caller can reset it to 1 to restart scanning of the same argv, or when scanning a new argument vector.

opterr: flag, 如果设置 opterr=0, 则不输出错误。

optopt: 遇到 optstring 中不存在的选项就保存在 optopt 中。

optstring 规则说明

"1abc:d:2::"

1,a,b: 只有选项，无选项参数
c,d: 必须要选项参数（选项和选项参数之间可以有空格）
2: 选项参数可选（可选选项如果选项和选项参数之间有空格，则被视为无选项参数）

返回值

If an option was successfully found, then getopt() returns the option character.
If all  command-line  options have  been  parsed,  then getopt() returns -1.
If getopt() encounters an option character that was not in optstring, then '?' is returned.
If getopt() encounters an option with a missing argument, then the return value depends on the first character in optstring:
    if it is ':', then ':' is returned; otherwise '?' is returned.

#include <unistd.h>
#include <iostream>

using namespace std;

#define OPTSTR  "1abc:d:2::"

int main(int argc, char *argv[])
{
    opterr = 0;
    int iRet = 0;
    int count = 0;
    cout << "optstring: " << OPTSTR << endl;
    cout << "BEGIN: optind=" << optind << endl;
    while ( (iRet = getopt(argc, argv, OPTSTR)) != -1 )
    {
        switch (iRet) 
        {
        case '1':
            cout << "-" << (char)iRet << ", value=" << (optarg ? optarg : "(no value)")
                << ", optind=" << optind << ", argv[optind-1]=" << argv[optind - 1] << endl;
            break;
        case 'a':
            cout << "-" << (char)iRet << ", value=" << (optarg ? optarg : "(no value)")
                << ", optind=" << optind << ", argv[optind-1]=" << argv[optind - 1] << endl;
            break;
        case 'b':
            cout << "-" << (char)iRet << ", value=" << (optarg ? optarg : "(no value)")
                << ", optind=" << optind << ", argv[optind-1]=" << argv[optind - 1] << endl;
            break;
        case 'c':
            cout << "-" << (char)iRet << ", value=" << (optarg ? optarg : "(no value)")
                << ", optind=" << optind << ", argv[optind-1]=" << argv[optind - 1] << endl;
            break;
        case 'd':
            cout << "-" << (char)iRet << ", value=" << (optarg ? optarg : "(no value)")
                << ", optind=" << optind << ", argv[optind-1]=" << argv[optind - 1] << endl;
            break;
        case '2':
            cout << "-" << (char)iRet << ", value=" << (optarg ? optarg : "(no value)")
                << ", optind=" << optind << ", argv[optind-1]=" << argv[optind - 1] << endl;
            break;
        default:    // '?'
            cout << "error: iRet=" << (char)iRet << ", optind=" << optind
                << ", optopt=" << (char)optopt << endl;
            break;
        }
        ++count;
    }
    cout << "count: " << count << endl;

    return 0;
}

/*
correct:
./test -1 -a -b -dvalue -cvalue  -2value
./test -1 -dvalue -2value
./test -1 -dvalue -2

./test -1 -a -b -d value -c value  -2value

wrong:
./test -1value
./test -x
*/

getopt_long()——既接受短选项，也接受长选项

长选项格式：--option value or --option=value

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

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

name: 长选项名称

has_arg: 选项类型，是否带参数

Symbolic constant	Numeric value	Meaning
no_argument	0	The option does not take an argument.
required_argument	1	The option requires an argument.
optional_argument	2	The option's argument is optional.

flag, val: 如果 flag 设置为 NULL, 则返回值为 val. 如果 flag 为非 NULL, 则返回值为0, flag 所指向的变量的值被设为 val. 

Typically, if flag is not NULL, then val is a true/false value, such as 1 or 0. On the other hand, if flag is NULL, then val is usually a character constant. 

如果一个选项既有长格式又有短格式（如 --help 和 -h），将 val 的值设为短格式的值（如 'h'）。

int do_all, do_help, do_verbose;    /* flag variables */
char *myfile;

struct option longopts[] = {
	{ "all",     no_argument,       & do_all,     1   },
	{ "file",    required_argument, NULL,         'f' },
	{ "help",    no_argument,       & do_help,    1   },
	{ "verbose", no_argument,       & do_verbose, 1   },
	{ 0, 0, 0, 0 }
};
...
while ((c = getopt_long(argc, argv, ":f:", longopts, NULL)) != -1) {
	switch (c)
	{
	case 'f':
		myfile = optarg;
		break;
	case 0:
		/* getopt_long() set a variable, just keep going */
		break;
	...               Error handling code here
	}
}

更过例子：

http://linux.die.net/man/3/getopt_long

http://www.informit.com/articles/article.aspx?p=175771&seqNum=3