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NAME

       fprintf, printf, snprintf, sprintf - print formatted output

SYNOPSIS

       #include <stdio.h>

       int fprintf(FILE *restrict stream, const char *restrict format, ...);
       int printf(const char *restrict format, ...);
       int snprintf(char *restrict s, size_t n,
              const char *restrict format, ...);
       int sprintf(char *restrict s, const char *restrict format, ...);

DESCRIPTION

       The  fprintf()  function shall place output on the named output stream.
       The printf() function shall place output on the standard output  stream
       stdout.  The sprintf() function shall place output followed by the null
       byte, ’\0’ , in consecutive bytes starting at  *s;  it  is  the  user’s
       responsibility to ensure that enough space is available.

       The  snprintf()  function  shall  be  equivalent to sprintf(), with the
       addition of the n argument which states the size of the buffer referred
       to  by  s.  If  n is zero, nothing shall be written and s may be a null
       pointer.  Otherwise, output bytes beyond the n-1st shall  be  discarded
       instead  of  being  written to the array, and a null byte is written at
       the end of the bytes actually written into the array.

       If copying takes place between objects that overlap as a  result  of  a
       call to sprintf() or snprintf(), the results are undefined.

       Each  of  these  functions  converts, formats, and prints its arguments
       under control  of  the  format.  The  format  is  a  character  string,
       beginning  and ending in its initial shift state, if any. The format is
       composed of zero or more directives:  ordinary  characters,  which  are
       simply copied to the output stream, and conversion specifications, each
       of which shall result in the fetching of zero or  more  arguments.  The
       results  are  undefined  if  there  are  insufficient arguments for the
       format. If the format is exhausted while arguments remain,  the  excess
       arguments shall be evaluated but are otherwise ignored.

       Conversions  can be applied to the nth argument after the format in the
       argument list, rather than to the next unused argument. In  this  case,
       the  conversion  specifier  character  % (see below) is replaced by the
       sequence  "%n$",  where  n  is  a  decimal   integer   in   the   range
       [1,{NL_ARGMAX}],  giving  the  position of the argument in the argument
       list. This feature provides for the definition of format  strings  that
       select arguments in an order appropriate to specific languages (see the
       EXAMPLES section).

       The  format   can   contain   either   numbered   argument   conversion
       specifications  (that  is,  "%n$"  and  "*m$"),  or unnumbered argument
       conversion specifications (that is, % and * ), but not both.  The  only
       exception  to  this  is  that  %% can be mixed with the "%n$" form. The
       results of mixing numbered and unnumbered argument specifications in  a
       format  string are undefined. When numbered argument specifications are
       used, specifying  the  Nth  argument  requires  that  all  the  leading
       arguments,  from  the first to the (N-1)th, are specified in the format
       string.

       In  format  strings   containing   the   "%n$"   form   of   conversion
       specification,   numbered   arguments  in  the  argument  list  can  be
       referenced from the format string as many times as required.

       In format strings containing the % form  of  conversion  specification,
       each  conversion  specification  uses  the first unused argument in the
       argument list.

       All forms of the fprintf() functions  allow  for  the  insertion  of  a
       language-dependent  radix  character  in  the  output string. The radix
       character is defined in the program’s locale (category LC_NUMERIC ). In
       the  POSIX  locale,  or  in  a  locale where the radix character is not
       defined, the radix character shall default to a period ( ’.’ ).

       Each conversion specification is introduced by the ’%’ character  or by
       the  character  sequence  "%n$",   after  which the following appear in
       sequence:

        * Zero or more flags (in any order), which modify the meaning  of  the
          conversion specification.

        * An  optional  minimum  field width. If the converted value has fewer
          bytes than the field width,  it  shall  be  padded  with  spaces  by
          default  on  the  left; it shall be padded on the right if the left-
          adjustment flag ( ’-’ ), described below,  is  given  to  the  field
          width.  The  field  width  takes  the  form  of an asterisk ( ’*’ ),
          described below, or a decimal integer.

        * An optional precision that gives the minimum  number  of  digits  to
          appear  for the d , i , o , u , x , and X conversion specifiers; the
          number of digits to appear after the radix character for the a , A ,
          e  ,  E  ,  f  ,  and F conversion specifiers; the maximum number of
          significant digits for the g and G  conversion  specifiers;  or  the
          maximum  number of bytes to be printed from a string in the s    and
          S   conversion specifiers. The precision takes the form of a  period
          (  ’.’ ) followed either by an asterisk ( ’*’ ), described below, or
          an optional decimal digit string,  where  a  null  digit  string  is
          treated  as  zero.  If a precision appears with any other conversion
          specifier, the behavior is undefined.

        * An optional length modifier that specifies the size of the argument.

        * A   conversion  specifier  character  that  indicates  the  type  of
          conversion to be applied.

       A field width, or precision, or both, may be indicated by an asterisk (
       ’*’ ). In this case an argument of type int supplies the field width or
       precision. Applications shall ensure that  arguments  specifying  field
       width,  or precision, or both appear in that order before the argument,
       if any, to be converted.  A negative field width is taken as a ’-’ flag
       followed by a positive field width. A negative precision is taken as if
       the precision were omitted.    In format strings containing  the  "%n$"
       form  of  a conversion specification, a field width or precision may be
       indicated by the sequence "*m$", where m is a decimal  integer  in  the
       range  [1,{NL_ARGMAX}]  giving the position in the argument list (after
       the format argument) of an integer argument containing the field  width
       or precision, for example:

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

       The flag characters and their meanings are:

       The integer portion of the result of a decimal conversion ( %i
              ,  %d  ,  %u  ,  %f  , %F , %g , or %G ) shall be formatted with
              thousands’  grouping  characters.  For  other  conversions   the
              behavior  is  undefined.  The non-monetary grouping character is
              used.

       -      The result of the conversion shall be left-justified within  the
              field.   The  conversion  is right-justified if this flag is not
              specified.

       +      The result of a signed conversion shall always begin with a sign
              ( ’+’ or ’-’ ). The conversion shall begin with a sign only when
              a negative value is converted if this flag is not specified.

       <space>
              If the first character of a signed conversion is not a  sign  or
              if a signed conversion results in no characters, a <space> shall
              be prefixed to the result. This means that if  the  <space>  and
              ’+’ flags both appear, the <space> flag shall be ignored.

       #      Specifies  that  the  value is to be converted to an alternative
              form.   For  o  conversion,  it  increases  the  precision   (if
              necessary)  to  force  the first digit of the result to be zero.
              For x or X conversion specifiers, a non-zero result  shall  have
              0x (or 0X) prefixed to it. For a , A , e , E , f , F , g , and G
              conversion specifiers, the result shall always contain  a  radix
              character, even if no digits follow the radix character. Without
              this flag, a radix character appears  in  the  result  of  these
              conversions  only  if a digit follows it. For g and G conversion
              specifiers, trailing zeros shall not be removed from the  result
              as  they  normally  are.   For  other conversion specifiers, the
              behavior is undefined.

       0      For d , i , o , u , x , X , a , A , e , E , f , F , g  ,  and  G
              conversion  specifiers,  leading zeros (following any indication
              of sign or base) are used to pad to the field  width;  no  space
              padding  is performed. If the ’0’ and ’-’ flags both appear, the
              ’0’ flag is ignored. For d , i , o , u , x ,  and  X  conversion
              specifiers,  if  a  precision  is  specified,  the  ’0’  flag is
              ignored.    If the ’0’ and ’" flags both  appear,  the  grouping
              characters   are   inserted   before  zero  padding.  For  other
              conversions, the behavior is undefined.

       The length modifiers and their meanings are:

       hh     Specifies that a following d , i , o , u , x , or  X  conversion
              specifier  applies  to  a  signed char or unsigned char argument
              (the argument will have been promoted according to  the  integer
              promotions,  but  its value shall be converted to signed char or
              unsigned char before printing); or that a following n conversion
              specifier applies to a pointer to a signed char argument.

       h      Specifies  that  a following d , i , o , u , x , or X conversion
              specifier applies to a short or  unsigned  short  argument  (the
              argument  will  have  been  promoted  according  to  the integer
              promotions, but  its  value  shall  be  converted  to  short  or
              unsigned   short   before  printing);  or  that  a  following  n
              conversion specifier applies to a pointer to a short argument.

       l (ell)
              Specifies that a following d , i , o , u , x , or  X  conversion
              specifier  applies  to  a long or unsigned long argument; that a
              following n conversion specifier applies to a pointer to a  long
              argument;  that  a following c conversion specifier applies to a
              wint_t argument; that a following s conversion specifier applies
              to  a  pointer  to  a  wchar_t  argument;  or has no effect on a
              following a , A , e , E , f , F , g , or G conversion specifier.

       ll (ell-ell)

              Specifies  that  a following d , i , o , u , x , or X conversion
              specifier applies to a long long or unsigned long long argument;
              or  that a following n conversion specifier applies to a pointer
              to a long long argument.

       j      Specifies that a following d , i , o , u , x , or  X  conversion
              specifier  applies to an intmax_t or uintmax_t argument; or that
              a following n conversion specifier applies to a  pointer  to  an
              intmax_t argument.

       z      Specifies  that  a following d , i , o , u , x , or X conversion
              specifier applies  to  a  size_t  or  the  corresponding  signed
              integer   type  argument;  or  that  a  following  n  conversion
              specifier  applies  to  a  pointer  to  a  signed  integer  type
              corresponding to a size_t argument.

       t      Specifies  that  a following d , i , o , u , x , or X conversion
              specifier applies to a ptrdiff_t or the  corresponding  unsigned
              type  argument;  or  that  a  following  n  conversion specifier
              applies to a pointer to a ptrdiff_t argument.

       L      Specifies that a following a , A , e , E , f , F  ,  g  ,  or  G
              conversion specifier applies to a long double argument.

       If  a  length modifier appears with any conversion specifier other than
       as specified above, the behavior is undefined.

       The conversion specifiers and their meanings are:

       d, i   The int argument shall be converted to a signed decimal  in  the
              style  "[-]dddd".  The precision specifies the minimum number of
              digits  to  appear;  if  the  value  being  converted   can   be
              represented  in  fewer digits, it shall be expanded with leading
              zeros. The default precision is 1. The result of converting zero
              with an explicit precision of zero shall be no characters.

       o      The  unsigned  argument  shall  be  converted  to unsigned octal
              format in the style "dddd". The precision specifies the  minimum
              number  of digits to appear; if the value being converted can be
              represented in fewer digits, it shall be expanded  with  leading
              zeros.  The  default  precision  is 1.  The result of converting
              zero with an explicit precision of zero shall be no  characters.

       u      The  unsigned  argument  shall  be converted to unsigned decimal
              format in the style "dddd". The precision specifies the  minimum
              number  of digits to appear; if the value being converted can be
              represented in fewer digits, it shall be expanded  with  leading
              zeros.  The  default  precision  is 1.  The result of converting
              zero with an explicit precision of zero shall be no  characters.

       x      The unsigned argument shall be converted to unsigned hexadecimal
              format in the style "dddd"; the letters "abcdef" are  used.  The
              precision  specifies  the minimum number of digits to appear; if
              the value being converted can be represented in fewer digits, it
              shall  be  expanded with leading zeros. The default precision is
              1. The result of converting zero with an explicit  precision  of
              zero shall be no characters.

       X      Equivalent  to  the  x conversion specifier, except that letters
              "ABCDEF" are used instead of "abcdef" .

       f, F   The double argument shall be converted to  decimal  notation  in
              the  style  "[-]ddd.ddd",  where  the number of digits after the
              radix character is equal to the precision specification. If  the
              precision  is  missing, it shall be taken as 6; if the precision
              is explicitly  zero  and  no  ’#’  flag  is  present,  no  radix
              character  shall  appear. If a radix character appears, at least
              one digit appears before  it.   The  low-order  digit  shall  be
              rounded in an implementation-defined manner.

       A double argument representing an infinity shall be converted in one of
       the styles "[-]inf" or "[-]infinity" ; which style  is  implementation-
       defined. A double argument representing a NaN shall be converted in one
       of the styles "[-]nan(n-char-sequence)" or "[-]nan" ; which style,  and
       the  meaning  of  any n-char-sequence, is implementation-defined. The F
       conversion specifier produces "INF" , "INFINITY" , or "NAN" instead  of
       "inf" , "infinity" , or "nan" , respectively.

       e, E   The   double   argument   shall   be   converted  in  the  style
              "[-]d.ddddd", where  there  is  one  digit  before  the  radix
              character  (which  is  non-zero if the argument is non-zero) and
              the number of digits after it is equal to the precision; if  the
              precision  is  missing, it shall be taken as 6; if the precision
              is zero and no ’#’ flag is present,  no  radix  character  shall
              appear.   The   low-order   digit   shall   be   rounded  in  an
              implementation-defined manner.  The E conversion specifier shall
              produce  a  number  with  ’E’  instead  of  ’e’  introducing the
              exponent. The exponent shall always contain at least two digits.
              If the value is zero, the exponent shall be zero.

       A double argument representing an infinity or NaN shall be converted in
       the style of an f or F conversion specifier.

       g, G   The double argument shall be converted in the style f or  e  (or
              in  the  style  F or E in the case of a G conversion specifier),
              with the precision specifying the number of significant  digits.
              If  an  explicit  precision is zero, it shall be taken as 1. The
              style used depends on the value converted; style e (or E ) shall
              be used only if the exponent resulting from such a conversion is
              less than -4 or greater than or equal to the precision. Trailing
              zeros  shall  be  removed  from  the  fractional  portion of the
              result; a radix character shall appear only if it is followed by
              a digit or a ’#’ flag is present.

       A double argument representing an infinity or NaN shall be converted in
       the style of an f or F conversion specifier.

       a, A   A double argument representing a floating-point number shall  be
              converted  in  the  style  "[-]0xh.hhhhd",  where there is one
              hexadecimal digit (which shall be non-zero if the argument is  a
              normalized  floating-point  number and is otherwise unspecified)
              before the decimal-point character and the number of hexadecimal
              digits  after  it is equal to the precision; if the precision is
              missing and FLT_RADIX is a power of 2, then the precision  shall
              be  sufficient  for an exact representation of the value; if the
              precision is missing and FLT_RADIX is not a power of 2, then the
              precision  shall  be  sufficient  to  distinguish values of type
              double, except that  trailing  zeros  may  be  omitted;  if  the
              precision is zero and the ’#’ flag is not specified, no decimal-
              point character shall appear. The letters "abcdef" shall be used
              for  a conversion and the letters "ABCDEF" for A conversion. The
              A conversion specifier  produces  a  number  with  ’X’  and  ’P’
              instead  of  ’x’  and ’p’ . The exponent shall always contain at
              least one digit, and only as many more digits  as  necessary  to
              represent  the decimal exponent of 2.  If the value is zero, the
              exponent shall be zero.

       A double argument representing an infinity or NaN shall be converted in
       the style of an f or F conversion specifier.

       c      The int argument shall be converted to an unsigned char, and the
              resulting byte shall be written.

       If an l (ell) qualifier  is  present,  the  wint_t  argument  shall  be
       converted as if by an ls conversion specification with no precision and
       an argument that points to a two-element array  of  type  wchar_t,  the
       first  element  of  which  contains  the  wint_t  argument  to  the  ls
       conversion specification and the second element contains  a  null  wide
       character.

       s      The  argument shall be a pointer to an array of char. Bytes from
              the array shall  be  written  up  to  (but  not  including)  any
              terminating  null  byte.  If the precision is specified, no more
              than that many bytes shall be written. If the precision  is  not
              specified  or  is  greater  than  the  size  of  the  array, the
              application shall ensure that the array contains a null byte.

       If an l (ell) qualifier is present, the argument shall be a pointer  to
       an  array  of  type  wchar_t.  Wide  characters from the array shall be
       converted to characters  (each  as  if  by  a  call  to  the  wcrtomb()
       function,  with  the  conversion state described by an mbstate_t object
       initialized to zero before the first wide character is converted) up to
       and   including  a  terminating  null  wide  character.  The  resulting
       characters shall be written up to (but not including)  the  terminating
       null  character  (byte).  If no precision is specified, the application
       shall ensure that the array  contains  a  null  wide  character.  If  a
       precision is specified, no more than that many characters (bytes) shall
       be written (including shift sequences, if any),  and  the  array  shall
       contain  a  null  wide  character  if,  to equal the character sequence
       length given by the precision, the function would need to access a wide
       character  one  past  the  end of the array. In no case shall a partial
       character be written.

       p      The argument shall be a  pointer  to  void.  The  value  of  the
              pointer  is  converted to a sequence of printable characters, in
              an implementation-defined manner.

       n      The argument shall be a pointer to  an  integer  into  which  is
              written the number of bytes written to the output so far by this
              call  to  one  of  the  fprintf()  functions.  No  argument   is
              converted.

       C      Equivalent to lc .

       S      Equivalent to ls .

       %      Print  a  ’%’  character; no argument is converted. The complete
              conversion specification shall be %% .

       If a conversion specification does not match one of  the  above  forms,
       the  behavior is undefined. If any argument is not the correct type for
       the corresponding conversion specification, the behavior is  undefined.

       In no case shall a nonexistent or small field width cause truncation of
       a field; if the result of a conversion is wider than the  field  width,
       the   field  shall  be  expanded  to  contain  the  conversion  result.
       Characters generated by  fprintf()  and  printf()  are  printed  as  if
       fputc() had been called.

       For  the  a  and A conversion specifiers, if FLT_RADIX is a power of 2,
       the value shall be correctly rounded to a hexadecimal  floating  number
       with the given precision.

       For  a  and  A  conversions,  if  FLT_RADIX is not a power of 2 and the
       result is not exactly representable in the given precision, the  result
       should be one of the two adjacent numbers in hexadecimal floating style
       with the given precision, with the extra  stipulation  that  the  error
       should have a correct sign for the current rounding direction.

       For  the e , E , f , F , g , and G conversion specifiers, if the number
       of significant decimal digits is at most DECIMAL_DIG, then  the  result
       should  be  correctly  rounded.  If  the  number of significant decimal
       digits is more  than  DECIMAL_DIG  but  the  source  value  is  exactly
       representable  with  DECIMAL_DIG  digits,  then the result should be an
       exact representation with trailing zeros. Otherwise, the  source  value
       is  bounded  by  two  adjacent  decimal  strings  L  <  U,  both having
       DECIMAL_DIG significant digits; the  value  of  the  resultant  decimal
       string  D  should  satisfy L <= D <= U, with the extra stipulation that
       the  error  should  have  a  correct  sign  for  the  current  rounding
       direction.

       The st_ctime and st_mtime fields of the file shall be marked for update
       between the call to a successful execution of fprintf() or printf() and
       the next successful completion of a call to fflush() or fclose() on the
       same stream or a call to exit() or abort().

RETURN VALUE

       Upon successful completion, the fprintf() and printf() functions  shall
       return the number of bytes transmitted.

       Upon  successful  completion,  the  sprintf() function shall return the
       number of bytes written to s, excluding the terminating null byte.

       Upon successful completion, the snprintf() function  shall  return  the
       number  of  bytes  that  would  be written to s had n been sufficiently
       large excluding the terminating null byte.

       If an output error was encountered,  these  functions  shall  return  a
       negative value.

       If  the  value  of  n is zero on a call to snprintf(), nothing shall be
       written, the number of bytes that would have been written  had  n  been
       sufficiently  large  excluding  the terminating null shall be returned,
       and s may be a null pointer.

ERRORS

       For the conditions under which fprintf()  and  printf()  fail  and  may
       fail, refer to fputc() or fputwc() .

       In addition, all forms of fprintf() may fail if:

       EILSEQ A  wide-character  code  that  does  not  correspond  to a valid
              character has been detected.

       EINVAL There are insufficient arguments.

       The printf() and fprintf() functions may fail if:

       ENOMEM Insufficient storage space is available.

       The snprintf() function shall fail if:

       EOVERFLOW
              The value of n is greater than {INT_MAX} or the number of  bytes
              needed  to  hold  the  output  excluding the terminating null is
              greater than {INT_MAX}.

       The following sections are informative.

EXAMPLES

   Printing Language-Independent Date and Time
       The following statement can be used to print  date  and  time  using  a
       language-independent format:

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

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

              "%s, %s %d, %d:%.2d\n"

       This example would produce the following message:

              Sunday, July 3, 10:02

       For German usage, format could be a pointer to the following string:

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

       This definition of format would produce the following message:

              Sonntag, 3. Juli, 10:02

   Printing File Information
       The  following  example prints information about the type, permissions,
       and number of links of a specific file in a directory.

       The first two calls to printf() use data decoded from a previous stat()
       call.   The  user-defined  strperm()  function  shall  return  a string
       similar to the one at the beginning of the  output  for  the  following
       command:

              ls -l

       The next call to printf() outputs the owner’s name if it is found using
       getpwuid(); the getpwuid() function shall  return  a  passwd  structure
       from  which  the name of the user is extracted. If the user name is not
       found, the program instead prints out the numeric value of the user ID.

       The  next  call  prints  out  the  group  name  if  it  is  found using
       getgrgid(); getgrgid() is very similar to  getpwuid()  except  that  it
       shall  return  group information based on the group number. Once again,
       if the group is not found, the program prints the numeric value of  the
       group for the entry.

       The final call to printf() prints the size of the file.

              #include <stdio.h>
              #include <sys/types.h>
              #include <pwd.h>
              #include <grp.h>

              char *strperm (mode_t);
              ...
              struct stat statbuf;
              struct passwd *pwd;
              struct group *grp;
              ...
              printf("%10.10s", strperm (statbuf.st_mode));
              printf("%4d", statbuf.st_nlink);

              if ((pwd = getpwuid(statbuf.st_uid)) != NULL)
                  printf(" %-8.8s", pwd->pw_name);
              else
                  printf(" %-8ld", (long) statbuf.st_uid);

              if ((grp = getgrgid(statbuf.st_gid)) != NULL)
                  printf(" %-8.8s", grp->gr_name);
              else
                  printf(" %-8ld", (long) statbuf.st_gid);

              printf("%9jd", (intmax_t) statbuf.st_size);
              ...

   Printing a Localized Date String
       The  following  example gets a localized date string. The nl_langinfo()
       function shall return the localized date string,  which  specifies  the
       order  and  layout  of  the  date.  The  strftime() function takes this
       information and, using the tm structure for values, places the date and
       time  information  into  datestring. The printf() function then outputs
       datestring and the name of the entry.

              #include <stdio.h>
              #include <time.h>
              #include <langinfo.h>
              ...
              struct dirent *dp;
              struct tm *tm;
              char datestring[256];
              ...
              strftime(datestring, sizeof(datestring), nl_langinfo (D_T_FMT), tm);

              printf(" %s %s\n", datestring, dp->d_name);
              ...

   Printing Error Information
       The following example uses fprintf()  to  write  error  information  to
       standard error.

       In  the  first  group  of calls, the program tries to open the password
       lock file named LOCKFILE. If the file already exists, this is an error,
       as  indicated  by  the  O_EXCL flag on the open() function. If the call
       fails, the program assumes that someone else is updating  the  password
       file, and the program exits.

       The  next  group  of  calls  saves  a  new password file as the current
       password file by creating a link between LOCKFILE and the new  password
       file PASSWDFILE.

              #include <sys/types.h>
              #include <sys/stat.h>
              #include <fcntl.h>
              #include <stdio.h>
              #include <stdlib.h>
              #include <unistd.h>
              #include <string.h>
              #include <errno.h>

              #define LOCKFILE "/etc/ptmp"
              #define PASSWDFILE "/etc/passwd"
              ...
              int pfd;
              ...
              if ((pfd = open(LOCKFILE, O_WRONLY | O_CREAT | O_EXCL,
                  S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) == -1)
              {
                  fprintf(stderr, "Cannot open /etc/ptmp. Try again later.\n");
                  exit(1);
              }
              ...
              if (link(LOCKFILE,PASSWDFILE) == -1) {
                  fprintf(stderr, "Link error: %s\n", strerror(errno));
                  exit(1);
              }
              ...

   Printing Usage Information
       The following example checks to make sure the program has the necessary
       arguments, and  uses  fprintf()  to  print  usage  information  if  the
       expected number of arguments is not present.

              #include <stdio.h>
              #include <stdlib.h>
              ...
              char *Options = "hdbtl";
              ...
              if (argc < 2) {
                  fprintf(stderr, "Usage: %s -%s <file\n", argv[0], Options); exit(1);
              }
              ...

   Formatting a Decimal String
       The  following  example prints a key and data pair on stdout.  Note use
       of the ’*’ (asterisk) in the format string; this  ensures  the  correct
       number  of  decimal  places  for  the  element  based  on the number of
       elements requested.

              #include <stdio.h>
              ...
              long i;
              char *keystr;
              int elementlen, len;
              ...
              while (len < elementlen) {
              ...
                  printf("%s Element%0*ld\n", keystr, elementlen, i);
              ...
              }

   Creating a Filename
       The following example creates  a  filename  using  information  from  a
       previous  getpwnam()  function  that returned the HOME directory of the
       user.

              #include <stdio.h>
              #include <sys/types.h>
              #include <unistd.h>
              ...
              char filename[PATH_MAX+1];
              struct passwd *pw;
              ...
              sprintf(filename, "%s/%d.out", pw->pw_dir, getpid());
              ...

   Reporting an Event
       The following example loops until an event has timed out.  The  pause()
       function  waits  forever  unless  it  receives  a signal. The fprintf()
       statement should never occur due  to  the  possible  return  values  of
       pause().

              #include <stdio.h>
              #include <unistd.h>
              #include <string.h>
              #include <errno.h>
              ...
              while (!event_complete) {
              ...
                  if (pause() != -1 || errno != EINTR)
                      fprintf(stderr, "pause: unknown error: %s\n", strerror(errno));
              }
              ...

   Printing Monetary Information
       The  following  example uses strfmon() to convert a number and store it
       as a formatted monetary string named convbuf. If the  first  number  is
       printed,  the program prints the format and the description; otherwise,
       it just prints the number.

              #include <monetary.h>
              #include <stdio.h>
              ...
              struct tblfmt {
                  char *format;
                  char *description;
              };

              struct tblfmt table[] = {
                  { "%n", "default formatting" },
                  { "%11n", "right align within an 11 character field" },
                  { "%#5n", "aligned columns for values up to 99999" },
                  { "%=*#5n", "specify a fill character" },
                  { "%=0#5n", "fill characters do not use grouping" },
                  { "%^#5n", "disable the grouping separator" },
                  { "%^#5.0n", "round off to whole units" },
                  { "%^#5.4n", "increase the precision" },
                  { "%(#5n", "use an alternative pos/neg style" },
                  { "%!(#5n", "disable the currency symbol" },
              };
              ...
              float input[3];
              int i, j;
              char convbuf[100];
              ...
              strfmon(convbuf, sizeof(convbuf), table[i].format, input[j]);

              if (j == 0) {
                  printf("%s  %s  %s\n", table[i].format,
                      convbuf, table[i].description);
              }
              else {
                  printf("    %s\n", convbuf);
              }
              ...

   Printing Wide Characters
       The following example prints a series of wide characters. Suppose  that
       "L@" expands to three bytes:

              wchar_t wz [3] = L"@@";       // Zero-terminated
              wchar_t wn [3] = L"@@@";      // Unterminated

              fprintf (stdout,"%ls", wz);   // Outputs 6 bytes
              fprintf (stdout,"%ls", wn);   // Undefined because wn has no terminator
              fprintf (stdout,"%4ls", wz);  // Outputs 3 bytes
              fprintf (stdout,"%4ls", wn);  // Outputs 3 bytes; no terminator needed
              fprintf (stdout,"%9ls", wz);  // Outputs 6 bytes
              fprintf (stdout,"%9ls", wn);  // Outputs 9 bytes; no terminator needed
              fprintf (stdout,"%10ls", wz); // Outputs 6 bytes
              fprintf (stdout,"%10ls", wn); // Undefined because wn has no terminator

       In  the  last  line  of the example, after processing three characters,
       nine bytes have been output. The fourth character must then be examined
       to  determine  whether it converts to one byte or more.  If it converts
       to more than one byte, the output is only nine bytes. Since there is no
       fourth character in the array, the behavior is undefined.

APPLICATION USAGE

       If  the application calling fprintf() has any objects of type wint_t or
       wchar_t, it must also  include  the  <wchar.h>  header  to  have  these
       objects defined.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       fputc()  ,  fscanf()  ,  setlocale() , strfmon() , wcrtomb() , the Base
       Definitions  volume  of  IEEE Std 1003.1-2001,   Chapter   7,   Locale,
       <stdio.h>, <wchar.h>

COPYRIGHT

       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .