C scanf() function

C library function - scanf()

The scanf() function is use to read data from the standard input stream stdin into the locations given by each entry in argument-list. Arguments must be pointers to variables whose types correspond to those in format-string. Input fields are interpreted by a format-string, which consists of a multibyte character string that begins and ends in a shift state.

Syntax:

int scanf(const char *format-string, argument-list);

Parameters:

The format is a character string, beginning and ending in its initial shift state, if any, composed of zero or more directives. Each directive is composed of one of the following: one or more white-space characters ( <space>, <tab>, <newline>, <vertical-tab>, or <form-feed>); an ordinary character; or a conversion specification. Each conversion specification is introduced by the character '%' or the character sequence "%n$", after which the following appear in sequence:

• An optional assignment-suppressing character '*'.
• An optional non-zero decimal integer that specifies the maximum field width.
• An optional assignment-allocation character 'm'.
• An option length modifier that specifies the size of the receiving object.
• A conversion specifier character that specifies the type of conversion to be applied. The valid conversion specifiers are described below.

The conversion characters and their meaning are shown in the following table:

Following table shows the length modifiers and their meanings:

Return value

• Upon successful completion, this function shall return the number of successfully matched and assigned input items; this number can be zero in the event of an early matching failure.

Example-1: scanf() function

#include <stdio.h>
int main(void)
{
   int item_id;
   float item_price;
   printf("Input item ID:\n");
   scanf("%d", &item_id);
   printf("Input item price:\n");
   scanf("%f", &item_price);
   fflush(stdin);
   printf("\nItem ID: %d", item_id);
   printf("\nItem price: %f ", item_price);
}

Output:

Input item ID:
123
Input item price:
225.60

Item ID: 123
Item price: 225.600006

Example-2: scanf() function:

Here is an example of how the scanf() function works when the width of input data is specified:

#include <stdio.h>
int main(void)
{
   int item_id;
   float item_price;
   printf("Input item ID:\n");
   scanf("%d", &item_id);
   printf("Input item price:\n");
   scanf("%f", &item_price);
   fflush(stdin);
   printf("\nItem ID: %d", item_id);
   printf("\nItem price: %f ", item_price);
}

Output of the said program for different values:

Input:
23445.34
test
Output:
23 445.339996 te
--------------------------
Input:
9 8764
test
Output:
9 8764.000000 te

It must be noted that when an user accept strings using scanf(), a space is considered to be a string terminator. Therefore, scanf() cannot be used to accept strings containing spaces unless the number of words is known. Consider the following example:

#include <stdio.h>
int main(void)
{
 char text[50];
 printf("Input a string (max 50 characters):\n");
 scanf("%50s", text);
 fflush(stdin);
 printf("Output:\n");
 printf("%s", text);
}

Output:

Input a string (max 50 characters):
C programming
Output:
C

There was a space after 'C' in the input, which caused the string to be terminated. In order to accept strings that may contain spaces, the gets() function should be used.

C Programming Code Editor:

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