Getting Into a Routine

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GETTING INTO A ROUTINE

Lessons from the Trenches Setting Up an Integer Print Routine

by George Martin

Start ı Determining Whatıs Needed ı A Definition ı For Argument's Sake ı The Code ı Sources and PDF

A DEFINITION

Microsoft Visual C++ V.5.0 describes sprintf as follows:

Return value

sprintf returns the number of bytes stored in the buffer, not counting the terminating null character.

Parameters

buffer Storage location for output format, Format-control string argument, Optional arguments

Remarks

The sprintf function formats and stores a series of characters and values in the buffer. Each argument (if any) is converted and output according to the corresponding format specification in the format. The format consists of ordinary characters and has the same form and function as the format argument for printf. A null character is appended after the last character written. If copying occurs between strings that overlap, the behavior is undefined.

Format specification fields: sprintf

A format specification, which consists of optional and required fields, has the following form:

%[flags] [width] [.precision] [{h | l | I64 | L}]type

Each field of the format specification is a single character or a number signifying a particular format option. The simplest format specification contains only the percent sign and a type character (for example, %s). If the percent sign is followed by a character that has no meaning as a format field, the character is copied to stdout. For example, to print a percent sign character, use %%.

The optional fields, which appear before the type character, control other aspects of the formatting, such as:

typeıRequired character that determines whether the associated argument is interpreted as a character, string, or number.
flagsıOptional character or characters that control justification of output and printing of signs, blanks, decimal points, and octal and hexadecimal prefixes. More than one flag can appear in a format specification.
widthıOptional number that specifies the minimum number of characters output.
precisionıOptional number that specifies the maximum number of characters printed for all or part of the output field or the minimum number of digits printed for integer values.
h | l | I64 | LıOptional prefixes to type, which specify the size of argument.

These routines are useful when formatting of the output messages is required. The printf routine copies characters directly to the stdout device, and the sprintf routine places the characters into a buffer. Then, you can decide what to do with that buffered data.

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