printf(3int)

Name

printf, fprintf, sprintf − print formatted output

Syntax

#include <stdio.h>

int printf ( format [, arg ] ... )
char *format;

int fprintf ( stream, format [, arg ] ... )
FILE *stream;
char *format;

int sprintf ( s, format [, arg ] ... )
char *s, format;

Description

The international functions printf, fprintf, and sprintf are similar to the printf standard I/O functions. The difference is that the international functions allow you to use the %digit$ conversion character in place of the % character you use in the standard I/O functions. The digit is a decimal digit n from 1 to 9. The international functions apply conversions to the n th argument in the argument list, rather than to the next unused argument.

You can use the % conversion character in the international functions. However, you cannot mix the % conversion character with the %digit$ conversion character in a single call.

You can indicate a field width or precision by an asterisk (*) instead of a digit string in format strings containing the % conversion character. If you use an asterisk, you can supply an integer arg that specifies the field width or precision. In format strings containing the %digit$ conversion character, you can indicate field width or precision by the sequence *digit$. You use a decimal digit from 1 to 9 to indicate which argument contains an integer that specifies the field width or precision.

The conversion characters and their meanings are identical to printf.

You must use each digit argument at least once.

In all cases, the radix character printf uses is defined by the last successful call to setlocale category LC_NUMERIC. If setlocale category LC_NUMERIC has not been called successfully or if the radix character is undefined, the radix character defaults to a period (.).

International Environment

LC_NUMERICIf this environment is set and valid, printf uses the international language database named in the definition to determine radix character rules.

LANGIf this environment variable is set and valid printf uses the international language database named in the definition to determine collation and character classification rules. If LC_NUMERIC is defined, its definition supercedes the definition of LANG.

Examples

The following example illustrates using an argument to specify field width:

printf ("%1$d:%2$.*3$d:%4$.*3$d\n",
hour, min, precision, sec);

The format string *3$ indicates that the third argument, which is named precision, contains the integer field width specification.

To print the language independent date and time format use the following printf statement:

printf (format, weekday, month, day, hour, min);

For American use, format could be a pointer to the following string:

"%1$s, %2$s %3$d, %4$d:%5$.2d\n"

This string gives the following date format:

Sunday, July 3, 10:02

For use in a German environment, format could be a pointer to the following string:

"%1$s, %3$d. %2$s, %4$d:%5$.2d\n"

This string gives the following date format:

Sonntag, 3. Juli, 10:02

Return Values

printf and fprintf return zero for success and EOF for failure. The sprintf subroutine returns its first argument for success and EOF for failure.

In the System V and POSIX environments, printf, fprintf, and sprintf return the number of characters transmitted for success. The sprintf function ignores the null terminator (\0) when calculating the number of characters transmitted. If an output error occurs, these routines return a negative value.

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