我知道应该使用getopt来解析命令行参数,而不是字符串。
然而,我感到困惑的是,如果我传递一个“看起来像”argv变量的字符串数组,getopt_long似乎可以工作,但只是我第一次调用它 。对于第二个以及随后的所有时间,我称之为忽略任何参数并返回默认参数。
我这样做的原因是我正在转变一个应用程序,该应用程序曾经在它的“交互”版本中接受命令行参数,要求用户提供一些参数,然后根据这些参数执行一些操作,然后请求更多的论据等等。
以下代码是重现错误的最小示例
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
struct input_parameters{
char * d; // data set
};
int solver_help(int argc, char* const argv[], struct input_parameters * p)
{
int c;
p->d = "default name";
while (1)
{
static struct option long_options[] =
{
{"data", required_argument, 0, 'd'},
{0, 0, 0, 0}
};
/* getopt_long stores the option index here. */
int option_index = 0;
c = getopt_long (argc, argv, "d:",
long_options, &option_index);
/* Detect the end of the options. */
if (c == -1)
break;
switch (c)
{
case 'd': p->d = optarg;
break;
default:
printf("wrong option specification\n");
exit(-1);
}
}
return 0 ;
}
int main () {
int argc_first = 3;
char * const argv_first[] = { "getopt_test", "--data", "first" };
struct input_parameters first_input;
solver_help(argc_first, argv_first, &first_input);
printf("I think the data is: %s\n", first_input.d);
int argc_second = 3;
char * const argv_second[] = { "getopt_test","--data", "second" };
struct input_parameters second_input;
solver_help(argc_second, argv_second, &second_input);
printf("I think the data is: %s\n", second_input.d);
return 0;
}
此代码的输出是
I think the data is: first
I think the data is: default name
答案 0 :(得分:3)
来自getopt
的手册页:
为了使用
getopt()
来评估多组参数,或者 多次评估一组参数,即变量 {2}之前必须将optreset
设置为1
一组对getopt()
的调用,变量optind
必须是 重新初始化。
稍微修改代码会为您提供所需的结果:
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
struct input_parameters {
char * d; // data set
};
int solver_help(int argc, char* const argv[], struct input_parameters * p)
{
p->d = "default name";
static struct option long_options[] =
{
{"data", required_argument, 0, 'd'},
{0, 0, 0, 0}
};
int option_index = 0;
optreset = 1; /* ADD THIS */
optind = 1; /* ADD THIS */
int c = getopt_long(argc, argv, "d:",
long_options, &option_index);
switch ( c )
{
case -1:
break;
case 'd':
p->d = optarg;
break;
default:
printf("in default case...\n");
printf("wrong option specification\n");
exit(EXIT_FAILURE);
}
return 0;
}
int main(void) {
int argc_first = 3;
char * const argv_first[] = { "getopt_test", "--data", "first" };
struct input_parameters first_input;
solver_help(argc_first, argv_first, &first_input);
printf("I think the data is: %s\n", first_input.d);
int argc_second = 3;
char * const argv_second[] = { "getopt_test","--data", "second" };
struct input_parameters second_input;
solver_help(argc_second, argv_second, &second_input);
printf("I think the data is: %s\n", second_input.d);
return 0;
}
带输出:
paul@horus:~/src/sandbox$ ./go
I think the data is: first
I think the data is: second
paul@horus:~/src/sandbox$