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.Dd December 6, 2023
.Dt STRFMON 3
.Os
.Sh NAME
.Nm strfmon ,
.Nm strfmon_l
.Nd convert monetary value to string
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In monetary.h
.Ft ssize_t
.Fn strfmon "char * restrict s" "size_t maxsize" "const char * restrict format" "..."
.In monetary.h
.In xlocale.h
.Ft ssize_t
.Fn strfmon_l "char * restrict s" "size_t maxsize" "locale_t loc" "const char * restrict format" "..."
.Sh DESCRIPTION
The
.Fn strfmon
function places characters into the array pointed to by
.Fa s ,
as controlled by the string pointed to by
.Fa format .
No more than
.Fa maxsize
bytes are placed into the array.
.Pp
The
.Fn strfmon_l
function takes an explicit locale argument, whereas the
.Fn strfmon
function uses the current global or per-thread locale.
.Pp
The format string is composed of zero or more directives:
ordinary characters (not
.Cm % ) ,
which are copied unchanged to the output stream; and conversion
specifications, each of which results in fetching zero or more subsequent
arguments.
Each conversion specification is introduced by the
.Cm %
character.
After the
.Cm % ,
the following appear in sequence:
.Bl -bullet
.It
Zero or more of the following flags:
.Bl -tag -width "XXX"
.It Cm = Ns Ar f
A
.Sq Cm =
character followed by another character
.Ar f
which is used as the numeric fill character.
.It Cm ^
Do not use grouping characters, regardless of the current locale default.
.It Cm +
Represent positive values by prefixing them with a positive sign,
and negative values by prefixing them with a negative sign.
This is the default.
.It Cm \&(
Enclose negative values in parentheses.
.It Cm \&!
Do not include a currency symbol in the output.
.It Cm \-
Left justify the result.
Only valid when a field width is specified.
.El
.It
An optional minimum field width as a decimal number.
By default, there is no minimum width.
.It
A
.Sq Cm #
sign followed by a decimal number specifying the maximum
expected number of digits before the radix character.
When this option is used, values that do not exceed the
specified number of digits are formatted so they will be
correctly aligned with other values printed using the same
format.
This includes always leaving space for a possible sign
indicator, even if none is needed for a particular value.
.It
A
.Sq Cm \&.
character followed by a decimal number specifying the number
of digits after the radix character.
.It
One of the following conversion specifiers:
.Bl -tag -width "XXX"
.It Cm i
The
.Vt double
argument is formatted as an international monetary amount.
.It Cm n
The
.Vt double
argument is formatted as a national monetary amount.
.It Cm %
A
.Sq Li %
character is written.
.El
.El
.Sh RETURN VALUES
If the total number of resulting bytes, including the terminating
.Dv NUL
byte, is not more than
.Fa maxsize ,
.Fn strfmon
and
.Fn strfmon_l
return the number of bytes placed into the array pointed to by
.Fa s ,
not including the terminating
.Dv NUL
byte.
Otherwise, \-1 is returned,
the contents of the array are indeterminate,
and
.Va errno
is set to indicate the error.
.Sh EXAMPLES
The following example will format the value
.Dq Li 1234567.89
to the string
.Dq Li $1,234,567.89 :
.Bd -literal -offset indent
#include <stdio.h>
#include <monetary.h>
#include <locale.h>

int
main(void)
{
	char string[100];
	double money = 1234567.89;

	if (setlocale(LC_MONETARY, "en_US.UTF-8") == NULL) {
		fprintf(stderr, "Unable to setlocale().\\n");
		return (1);
	}

	strfmon(string, sizeof(string) - 1, "%n", money);
	printf("%s\\n", string);

	return (0);
}
.Ed
.Sh ERRORS
The
.Fn strfmon
function will fail if:
.Bl -tag -width Er
.It Bq Er E2BIG
Conversion stopped due to lack of space in the buffer.
.It Bq Er EINVAL
The format string is invalid.
.It Bq Er ENOMEM
Not enough memory for temporary buffers.
.El
.Sh SEE ALSO
.Xr localeconv 3 ,
.Xr xlocale 3
.Sh STANDARDS
The
.Fn strfmon
function
conforms to
.St -p1003.1-2001 .
The
.Fn strfmon_l
function conforms to
.St -p1003.1-2008 .
.Sh AUTHORS
.An -nosplit
The
.Fn strfmon
function was implemented by
.An Alexey Zelkin Aq Mt phantom@FreeBSD.org .
.Pp
This manual page was written by
.An Jeroen Ruigrok van der Werven Aq Mt asmodai@FreeBSD.org
based on the standards' text.
.Sh BUGS
The
.Fn strfmon
function does not correctly handle multibyte characters in the
.Fa format
argument.