C++ scanf()

#include <cstdio>
#include <iostream>
using namespace std;

int main() {
  int age;

  cout << "Enter your age: ";

  // get age from user
  scanf("%d", &age);

  // print age
  cout << "Age = " << age;
    
  return 0;
}

Enter your age: 39
Age = 39

scanf() Syntax

The syntax of scanf() is:

scanf(const char* format, ...);

scanf() Parameters

The scanf() function takes the following parameters:

• format - pointer to a C-string that specifies how to read the input. It consists of format specifiers starting with %.

• ... - other additional arguments specifying the data to be printed. They occur in a sequence according to the format specifier.

scanf() Return Value

• If successful, it returns the number of receiving arguments successfully assigned.
• If a matching failure occurs before the first receiving argument was assigned, returns 0.
• If input failure occurs before the first receiving argument was assigned, EOF is returned.

scanf() Prototype

The prototype of the scanf() function as defined in the cstdio header file is:

int scanf(const char* format, ...);

Format String

The format parameter of scanf() can contain format specifiers that begin with %. The format string has the following parts:

• Non whitespace characters except % each of which consumes one identical character from the input stream. It can cause the function to fail if the next character on the stream does not compare equal.
• Whitespace character - All the consecutive whitespace characters are treated as a single whitespace character. Further, '\n', '\t' and ' ' are considered the same.
• Conversion specification - It follows the following format:
  • Initial % character that specifies the beginning.
  • An optional * called assignment-suppression character. If this character is present, scanf() does not assign the result to any receiving argument.
  • width - an optional positive integer number that specifies maximum field width. It specifies the maximum number of characters that scanf() is allowed to consume when doing the conversion specified by the current conversion specification.
  • length - an optional length modifier specifying the size of the receiving argument.
  • specifier - a conversion format specifier.
• ... - other additional arguments for receiving data. They occur in a sequence according to the format specifier.

scanf() Format Specifier Prototype

The general format of format specifier for scanf() is:

%[*][width][length]specifier

Common Format Specifiers

Example: C++ scanf()

#include <cstdio>

int main () {
  char name[50];
  int age;
    
  printf("Enter your name: ");

  // get user input for name
  scanf("%s", name);

  printf("Enter your age: ");

  // get user input for age
  scanf("%d", &age);

  // print name and age
  printf("Hello %s, you are %d years old.", name, age);

  return 0;
}

Output

Enter your name: Tim
Enter your age: 31
Hello Tim, you are 31 years old.