Wednesday, November 2, 2011

sprintf( ) and sscanf( ) Functions in C programming language

The sprintf( ) function works similar to the printf( ) function except for one small difference. Instead of sending the output to the screen as printf( ) does, this function writes the output to an array of characters. The following program illustrates this.

main( )
{
int i = 10 ;
char ch = 'A' ;
float a = 3.14 ;
char str[20] ;
printf ( "\n%d %c %f", i, ch, a ) ;
sprintf ( str, "%d %c %f", i, ch, a ) ;
printf ( "\n%s", str ) ;
}

In this program the printf( ) prints out the values of i, ch and a on the screen, whereas sprintf( ) stores these values in the character array str. Since the string str is present in memory what is written into str using sprintf( ) doesn’t get displayed on the screen. Once str has been built, its contents can be displayed on the screen. In our program this was achieved by the second printf( ) statement.
The counterpart of sprintf( ) is the sscanf( ) function. It allows us to read characters from a string and to convert and store them in C variables according to specified formats. The sscanf( ) function comes in handy for in-memory conversion of characters to values. You may find it convenient to read in strings from a file and then extract values from a string by using sscanf( ). The usage of sscanf( ) is same as scanf( ), except that the first argument is the string from which reading is to take place.

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