STRFMON(3)             FreeBSD Library Functions Manual             STRFMON(3)

NAME

     strfmon, strfmon_l - convert monetary value to string

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <monetary.h>

     ssize_t
     strfmon(char * restrict s, size_t maxsize, const char * restrict format,
         ...);

     #include <monetary.h>
     #include <xlocale.h>

     ssize_t
     strfmon_l(char * restrict s, size_t maxsize, locale_t loc,
         const char * restrict format, ...);

DESCRIPTION

     The strfmon() function places characters into the array pointed to by s,
     as controlled by the string pointed to by format.  No more than maxsize
     bytes are placed into the array.

     The strfmon_l() function takes an explicit locale argument, whereas the
     strfmon() function uses the current global or per-thread locale.

     The format string is composed of zero or more directives: ordinary
     characters (not %), 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
     % character.  After the %, the following appear in sequence:

     o   Zero or more of the following flags:

         =f   A `=' character followed by another character f which is used as
              the numeric fill character.

         ^    Do not use grouping characters, regardless of the current locale
              default.

         +    Represent positive values by prefixing them with a positive
              sign, and negative values by prefixing them with a negative
              sign.  This is the default.

         (    Enclose negative values in parentheses.

         !    Do not include a currency symbol in the output.

         -    Left justify the result.  Only valid when a field width is
              specified.

     o   An optional minimum field width as a decimal number.  By default,
         there is no minimum width.

     o   A `#' 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.

     o   A `.' character followed by a decimal number specifying the number of
         digits after the radix character.

     o   One of the following conversion specifiers:

         i    The double argument is formatted as an international monetary
              amount.

         n    The double argument is formatted as a national monetary amount.

         %    A `%' character is written.

RETURN VALUES

     If the total number of resulting bytes, including the terminating NUL
     byte, is not more than maxsize, strfmon() and strfmon_l() return the
     number of bytes placed into the array pointed to by s, not including the
     terminating NUL byte.  Otherwise, -1 is returned, the contents of the
     array are indeterminate, and errno is set to indicate the error.

EXAMPLES

     The following example will format the value "1234567.89" to the string
     "$1,234,567.89":

           #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);
           }

ERRORS

     The strfmon() function will fail if:

     [E2BIG]            Conversion stopped due to lack of space in the buffer.

     [EINVAL]           The format string is invalid.

     [EINVAL]           The + flag was included in a conversion specification
                        and the locale's positive_sign and negative_sign
                        values would both be returned by localeconv(3) as
                        empty strings.

     [ENOMEM]           Not enough memory for temporary buffers.

SEE ALSO

     localeconv(3), xlocale(3)

STANDARDS

     The strfmon() function conforms to IEEE Std 1003.1-2001 ("POSIX.1").  The
     strfmon_l() function conforms to IEEE Std 1003.1-2008 ("POSIX.1").

AUTHORS

     The strfmon() function was implemented by Alexey Zelkin
     <phantom@FreeBSD.org>.

     This manual page was written by Jeroen Ruigrok van der Werven
     <asmodai@FreeBSD.org> based on the standards' text.

BUGS

     The strfmon() function does not correctly handle multibyte characters in
     the format argument.

FreeBSD 15.1-STABLE-HBSD       November 24, 2025                    STRFMON(3)