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Learn more about: Argument Description |
Argument Description |
11/04/2016 |
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91c2cbe3-9aca-4277-afa1-6137eb8fb704 |
The argc parameter in the main and wmain functions is an integer specifying how many arguments are passed to the program from the command line. Since the program name is considered an argument, the value of argc is at least one.
The argv parameter is an array of pointers to null-terminated strings representing the program arguments. Each element of the array points to a string representation of an argument passed to main (or wmain). (For information about arrays, see Array Declarations.) The argv parameter can be declared either as an array of pointers to type char (char *argv[]) or as a pointer to pointers to type char (char **argv). For wmain, the argv parameter can be declared either as an array of pointers to type wchar_t (wchar_t *argv[]) or as a pointer to pointers to type wchar_t (wchar_t **argv).
By convention, argv[0] is the command with which the program is invoked. However, it is possible to spawn a process using CreateProcess and if you use both the first and second arguments (lpApplicationName and lpCommandLine), argv[0] may not be the executable name; use GetModuleFileName to retrieve the executable name.
The last pointer (argv[argc]) is NULL. (See getenv in the Run-Time Library Reference for an alternative method for getting environment variable information.)
Microsoft Specific
The envp parameter is a pointer to an array of null-terminated strings that represent the values set in the user's environment variables. The envp parameter can be declared as an array of pointers to char (char *envp[]) or as a pointer to pointers to char (char **envp). In a wmain function, the envp parameter can be declared as an array of pointers to wchar_t (wchar_t *envp[]) or as a pointer to pointers to wchar_t (wchar_t **envp). The end of the array is indicated by a NULL *pointer. Note that the environment block passed to main or wmain is a "frozen" copy of the current environment. If you subsequently change the environment via a call to _putenv or _wputenv, the current environment (as returned by getenv/_wgetenv and the _environ or _wenviron variables) will change, but the block pointed to by envp will not change. The envp parameter is ANSI compatible in C, but not in C++.
END Microsoft Specific