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  -2valuewrong:./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