how to get multiple input in C language? - c

Question

I'm new in C and would love to get some help regarding multipule input
for example I have this struct:
typedef struct person{
char * name;
int age;
}
and I want to write a function that get's :name age name age name age...
Is there a way I can do that ? how can I later get the values?
I mean something like :
void my_func(char* name, int age , char* name1,int age1.....)
like in JAVA I can use "..."
I want to do something like that :
void my_func(char* name, int age , char* name1,int age1.....){
int num_of_ppl = length of the input/2
person p1 ;
p1.name = first input name
p1.age = first input age
etc..
thanks!

Answer 1

You can use the vararg functionality in stdarg.h:
//
// First argument specifies the number of name/age pairs supplied
//
void my_func(int persons, char *name1, int age1, ...) {
int age, i;
char *name;
va_list vl;
va_start(vl, age1);
for (i = 1; i < persons; i++) {
name = va_arg(vl, char*);
age = va_arg(vl, int);
// Do something with the values
}
va_end(vl);
}

Answer 2

If you want a function with variable argument list you can use va_list
#include <cstdarg>
using namespace std;
void myFunction(int num, ...)
{
va_list arguments; // A place to store the list of arguments
va_start ( arguments, num ); // Initializing arguments to store all values after num
for ( int x = 0; x < num; x++ ) // Loop until all numbers are added
func(va_arg ( arguments, person )); // get next value of argument and call a function
va_end ( arguments ); // Cleans up the list
}

Answer 3

The C language is a very low-level language, so you'll need to decide how to handle each field.
In your case you need to decide what is the name, who owns the pointed data, and code appropriately, perhaps something like:
typedef struct person_st {
char* name; // malloc-ed string
int age;
} Person;
// allocate a Person of given name and age
Person* make_person(const char* n, int a) {
if (!n || a<0) return NULL;
Person* p = malloc(sizeof(Person));
if (!p)
perror("malloc Person"), exit(1);
p->name = strdup(n);
if (!p->name)
perror("strdup Person"), exit(1);
p->age = a;
return p;
}
// destroy a Person and the data inside
void destroy_person(Person*p) {
if (!p) return;
free (p->name);
free (p);
}
// read and allocate a Person
Person* input_person(FILE*f) {
if (!f) return NULL;
char name[104];
int age;
memset (name, 0, sizeof(name));
age = 0;
if (fscanf(f, " %100[A-Za-z] %d", &name, &age)<2)
return NULL;
return make_person(name, age);
}
with the convention that the caller of input_person should call destroy_person appropriately.
I might have misunderstood your question. Do you want to code simply a variadic function (which has no relation to input or output)? Then use carefully <stdarg.h> header. Be aware that variadic functions are poorly typed in C. With GCC, you can give the sentinel function attribute, and you could even customize GCC e.g. with MELT to add some type checking.