sprintf() prototype
int sprintf( char* buffer, const char* format, ... );
The sprintf()
function writes the string pointed to by format to buffer. The string format may contain format specifiers starting with % which are replaced by the values of variables that are passed to the sprintf()
function as additional arguments.
It is defined in <cstdio> header file.
sprintf() Parameters
- buffer: Pointer to the string buffer to write the result.
- format: Pointer to a null terminated string that is written to the file stream. It consists of characters along with optional format specifiers starting with %.
The format specifiers are replaced by the values of respective variables that follows the format string.
The format specifier has the following parts:
- A leading % sign
- Flags: Optional one or more flags that modifies the conversion behavior.
- - : Left justify the result within the field. By default it is right justified.
- + : The sign of the result is attached to the beginning of the value, even for positive results.
- Space: If there is no sign, a space is attached to the beginning of the result.
- # : An alternative form of the conversion is performed.
- 0 : It is used for integer and floating point number. Leading zeros are used to pad the numbers instead of space.
- Width: An optional * or integer value used to specify minimum width field.
- Precision : An optional field consisting of a . followed by * or integer or nothing to specify the precision.
- Length : An optional length modifier that specifies the size of the argument.
- Specifier: A conversion format specifier. The available format specifiers are as follows:
Format Specifier Description % Prints % c Writes a single character s Writes a character string d or i Converts a signed integer to decimal representation o Converts an unsigned integer to octal representation X or x Converts an unsigned integer to hexadecimal representation u Converts an unsigned integer to decimal representation F or f Converts floating-point number to the decimal representation E or e Converts floating-point number to the decimal exponent notation A or a Converts floating-point number to the hexadecimal exponent G or g Converts floating-point number to either decimal or decimal exponent notation n Returns the number of characters written so far by this call to the function. The result is written to the value pointed to by the argument p Writes an implementation defined character sequence defining a pointer. So the general format of format specifier is:
%[flags][width][.precision][length]specifier
- … : Other additional arguments specifying the data to be printed. They occur in a sequence according to the format specifier.
sprintf() Return value
- If successful, the
sprintf()
function returns number of characters that would have been written for sufficiently large buffer excluding the terminating null character. - On failure it returns a negative value.
Example: How sprintf() function works
#include <cstdio>
#include <iostream>
using namespace std;
int main()
{
char buffer[100];
int retVal;
char name[] = "Max";
int age = 23;
retVal = sprintf(buffer, "Hi, I am %s and I am %d years old", name, age);
cout << buffer << endl;
cout << "Number of characters written = " << retVal << endl;
return 0;
}
When you run the program, the output will be:
Hi, I am Max and I am 23 years old Number of characters written = 34