检查 argv[i] 是否存在 C++
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Checking if argv[i] exists C++
提问by thisiscrazy4
If I ran a C++ program
如果我运行一个 C++ 程序
./program arg1
argv[1] exists, however is there a way to check if argv[2] exists?
argv[1] 存在，但是有没有办法检查 argv[2] 是否存在？
回答by NPE
Yes, look at the value of argc:
是的，看看 的值argc：
if (argc > 2) {
... use argv[2] ...
}
回答by Grijesh Chauhan
Yes, argv[i]ends with NULL. argcis number of argumentspassed to main function. Get an idea from following code.
是的，argv[i]以NULL. argc被number of arguments传递给主函数。从以下代码中获取想法。
#include<stdio.h>
int main(int argc, char* argv[]){
int i=0;
while(argv[i]!=NULL){
printf("\n %s is argv %d ",argv[i],i);
i++;
}
printf("\n");
}
desktop:~$ gcc main.c -o main
desktop:~$ ./main grijesh thisiscrazy4
./main is argv 0
grijesh is argv 1
thisiscrazy4 is argv 2
here argv was - "./main","grijesh","thisiscrazy4",NULLand argc = 3.
这里 argv 是 -"./main","grijesh","thisiscrazy4",NULL并且 argc = 3。
argv[0]is executable name (path of execution) can be use to pint with error statements.argvcalled argument vector and argccalled argument counter. you can use other variable name also.
argv[0]是可执行名称（执行路径）可用于品脱错误语句。argv称为参数向量，argc称为参数计数器。您也可以使用其他变量名称。
Read about full syntax of main() functionthat also includes environment variables.
阅读包含环境变量的 main() 函数的完整语法。
int main (int argc, char *argv[], char *envp[])
{
return 0;
}
回答by Abhineet
The prototype of mainsays it all:
的原型main说明了一切：
int main(int argc, char **argv);
The first parameter here, argccarries the value of Number_Of_Arguments(argv[])_Present
这里的第一个参数，argc携带值Number_Of_Arguments(argv[])_Present
回答by Mahesh
You can try the other way around. Test the count of argc, there by you can know the presence of argv[n].
你可以换个方式试试。测试计数argc，通过你可以知道的存在argv[n]。
