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How to read data using sscanf() in C

Educative Answers Team

In C, sscanf() is used to read formatted data. It works much like scanf() but the data will be read from a string instead of the console.

How do we use this function?

In order to read formatted data from a string, first, we must know the syntax of the function, which is shown below.

Syntax

#include<stdio.h>

int main() {
    int sscanf(const char *read, const char *format,. . ., 
                storage_variables )
}
This function can only be used when the stdio.h library is included

Now let’s look at what parameters does this function take and what it returns.

Parameters

  • read: This is the pointer to the string that is to be read.

  • storage_variables Additional argument(s) that the function can take in order to store the value that is being read from the pointer. Here, if the value is being stored in a regular variable and not a pointer then the variable name must be preceded by the & sign.

  • format: These are the format specifiers according to which the data will be read from the input string.

Format Specifiers

A format specifier is a unique set of characters which is used to format the data being read in a certain way. It is preceded by a % sign and then the relevant symbol. The symbols are as follows:

Symbol Type
s string
c single character
d decimal integer
e, E, f, g, G floating points
u unsigned integer
x, X hexadecimal number

Return Value

  1. The function returns an int value which represents the total number of items read.
  2. Given there was an error and the string could not be read, an EOF error is returned.
  3. Any other type of error which is encountered while reading is denoted by the function returning -1.

Now that we know about the syntax, let’s look at a few examples to better understand sscanf().

Examples

1. Reading one item of the same type

The first example shows you how to read just a single data type in an input string.

#include<stdio.h>

int main() {
    char* buffer = "Hello";
    char store_value[10];
    int total_read;

    total_read = sscanf(buffer, "%s" , store_value);

    printf("Value in buffer: %s",store_value);
    printf("\nTotal items read: %d",total_read);

    return 0;
}

2. Reading multiple items of the same type

The example below shows how to read a space separated two words long string into two separate variables.

#include<stdio.h>

int main() {
    char* buffer = "Hello World";
    char store_hello[10], store_world[10];
    int total_read;

    total_read = sscanf(buffer, "%s %s" , store_hello, store_world);

    printf("Value in first variable: %s",store_hello);
    printf("\nValue in second variable:  %s",store_world);
    printf("\nTotal items read: %d",total_read);
    return 0;
}

3. Reading multiple items of different types

The example below shows how to read a string and an integer from the same buffer value.

#include<stdio.h>

int main() {
    char* buffer = "Hello 20";
    char store_string[10];
    int store_integer;
    int total_read;

    total_read = sscanf(buffer, "%s %d" , store_string, &store_integer);

    printf("String value in buffer: %s" ,store_string);
    printf(" \nInteger value in buffer: %d",store_integer);
    printf("\nTotal items read: %d",total_read);
    return 0;
}

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formatted data
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