sprintf Write formatted data to string
Writes into the array pointed by str a C string consisting on a sequence of data formatted as the format argument specifies. After the format parameter, the function expects at least as many additional arguments as specified in format.
This function behaves exactly as printf does, but writing its results to a string instead of stdout. The size of the array passed as str should be enough to contain the entire formatted string.
int sprintf ( char * str, const char * format, ... );
- Pointer to an array of char elements where the resulting C string is stored.
- C string that contains the text to be written to the buffer.
can optionally contain embedded format tags that are substituted by the
values specified in subsequent argument(s) and formatted as requested.
The number of arguments following the format parameters should at least be as much as the number of format tags.
The format tags follow this prototype:
Where specifier is the most significant one and defines the type and the interpretation of the value of the coresponding argument:
|d or i||Signed decimal integer||392|
|e||Scientific notation (mantise/exponent) using e character||3.9265e+2|
|E||Scientific notation (mantise/exponent) using E character||3.9265E+2|
|f||Decimal floating point||392.65|
|g||Use the shorter of %e or %f||392.65|
|G||Use the shorter of %E or %f||392.65|
|s||String of characters||sample|
|u||Unsigned decimal integer||7235|
|x||Unsigned hexadecimal integer||7fa|
|X||Unsigned hexadecimal integer (capital letters)||7FA|
|n||Nothing printed. The argument must be a pointer to a signed int, where the number of characters written so far is stored.|| |
|%||A % followed by another % character will write % to the string.|
The tag can also contain flags, width, .precision and modifiers sub-specifiers, which are optional and follow these specifications:
|-||Left-justify within the given field width; Right justification is the default (see width sub-specifier).|
|+||Forces to preceed the result with a plus or minus sign (+ or -) even for positive numbers. By default, only negative numbers are preceded with a - sign.|
|(space)||If no sign is going to be written, a blank space is inserted before the value.|
|#||Used with o, x or X specifiers the value is preceeded with 0, 0x or 0X respectively for values different than zero.|
Used with e, E and f,
it forces the written output to contain a decimal point even if no
digits would follow. By default, if no digits follow, no decimal point
Used with g or G the result is the same as with e or E but trailing zeros are not removed.
|0||Left-pads the number with zeroes (0) instead of spaces, where padding is specified (see width sub-specifier).|
|(number)||Minimum number of characters to be
printed. If the value to be printed is shorter than this number, the
result is padded with blank spaces. The value is not truncated even if
the result is larger.|
|*||The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.|
|.number||For integer specifiers (d, i, o, u, x, X): precision
specifies the minimum number of digits to be written. If the value to
be written is shorter than this number, the result is padded with
leading zeros. The value is not truncated even if the result is longer.
A precision of 0 means that no character is written for the value 0.|
For e, E and f specifiers: this is the number of digits to be printed after the decimal point.
For g and G specifiers: This is the maximum number of significant digits to be printed.
this is the maximum number of characters to be printed. By default all
characters are printed until the ending null character is encountered.
For c type: it has no effect.
When no precision is specified, the default is 1. If the period is specified without an explicit value for precision, 0 is assumed.
|.*||The precision is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.|
|h||The argument is interpreted as a short int or unsigned short int (only applies to integer specifiers: i, d, o, u, x and X).|
|l||The argument is interpreted as a long int or unsigned long int for integer specifiers (i, d, o, u, x and X), and as a wide character or wide character string for specifiers c and s.|
|L||The argument is interpreted as a long double (only applies to floating point specifiers: e, E, f, g and G). |
- additional arguments
- Depending on the format string, the function may expect a sequence of additional arguments, each containing one value to be inserted instead of each %-tag specified in the format parameter, if any. There should be the same number of these arguments as the number of %-tags that expect a value.
On success, the total number of characters written is returned. This
count does not include the additional null-character automatically
appended at the end of the string.
On failure, a negative number is returned.
/* sprintf example */
int main ()
char buffer ;
printf ("[%s] is a %d char long string\n",buffer,strlen(buffer));
[5 plus 3 is 8] is a 13 char long string