How can you pass variable arguments to a function in c?

Answer 1

## posted BY Pulkit ok. so to declare variable argements in arguments use this: ret_type function_name( . . .); using these three dots will tell compiler to include variable aarguments. Note: this feature has been included in New version of C,, this is not available in old compiler. thankx guys n grls ## posted BY Pulkit ok. so to declare variable argements in arguments use this: ret_type function_name( . . .); using these three dots will tell compiler to include variable aarguments. Note: this feature has been included in New version of C,, this is not available in old compiler. thankx guys n grls

Answer 2

By reference or by pointer, never by value. Passing by value would require the string to be copied, which is detrimental to performance. If the reference or pointer is constant, no changes will be made to the string, so its safe to pass a reference or pointer. If it is non-constant, this implies the string will be altered, so if you do not want the original string altered, you must copy the string and pass a reference or pointer to the copy instead. Some functions may provide a pass by value overload to cater for this, but that's an exception rather than a rule.

Remember that strings are nothing more than arrays of char (or wide char if using UNICODE), so they can be passed to functions just as you would any other type of array. When passing pointers, however, be sure the string is null-terminated, otherwise you must pass the string's length as well to avoid a buffer overrun.

Functions that operate on strings often provide several overloads to cater for all the different ways you might pass string, both with and without a buffer length. When creating user-defined functions that accept strings, this isn't really necessary, so long as you pass strings to those functions in a consistent way. However, if your functions will be distributed to third-parties, its best to provide fully-overloaded methods.

Generally, a string pointer is passed to a function as const char * (constant pointer) or just char * (non-constant pointer). However, you may have access to other typedefs for a string, including object references such as CString, or string templates such as CStringT. Regardless, they all boil down to an array of characters.

Answer 3

You pass parameters (or arguments) to the main function via command-line switches.

int main (int argc, char* argv[]) {

/* ... */

return 0;

}

The argv argument is a null-terminated array of null-terminated strings while argc holds the count of strings. The argc argument is always at least 1 because the first argument (argv[0]) is always the program name while argv[argc] is always null.

If your program is called my_prog.exe, then you can pass arguments to it from the command line like so:

my_prog arg1 arg2 arg3

Note that whitespace separates each argument.

Your main function will then hold the following values:

argc = 4

argv[0] = "<path>\my_prog.exe"

argv[1] = "arg1"

argv[2] = "arg2"

argv[3] = "arg3"

argv[4] = null

As programmer, it is your job to parse the command line and check for input errors before processing the switches and taking the appropriate action(s).

Answer 4

operating systme call the main function in c

execution start from main and ends with main