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FPRINTF(P)		   POSIX Programmer's Manual		    FPRINTF(P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the	 corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

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, begin‐
       ning and ending in its initial shift state, if any. The format is  com‐
       posed 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  for‐
       mat.  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 specifica‐
       tions (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  specifica‐
       tion,  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  lan‐
       guage-dependent radix character in the output string. The radix charac‐
       ter 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 sig‐
	  nificant digits for the g and G conversion specifiers; or the	 maxi‐
	  mum  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  conver‐
	  sion 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 thou‐
	      sands' 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 neces‐
	      sary) 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  con‐
	      version  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 con‐
	      versions 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  conver‐
	      sions, 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 promo‐
	      tions,  but  its	value  shall be converted to short or unsigned
	      short before printing); or that a following n conversion	speci‐
	      fier 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  fol‐
	      lowing 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	 inte‐
	      ger  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 con‐
	      version 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	repre‐
	      sented 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 for‐
	      mat 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  charac‐
	      ter  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.ddde±dd", where there is one digit before the radix	 char‐
	      acter  (which  is	 non-zero if the argument is non-zero) and the
	      number of digits after it is equal to the precision; if the pre‐
	      cision  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 implementa‐
	      tion-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.hhhhp±d",  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 dou‐
	      ble, 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 con‐
	      version 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  con‐
       verted 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 termi‐
	      nating null byte. If the precision is specified,	no  more  than
	      that many bytes shall be written. If the precision is not speci‐
	      fied 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  con‐
       verted  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 includ‐
       ing 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 char‐
       acter if, to equal the character sequence length given  by  the	preci‐
       sion,  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  con‐
	      verted.

       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.  Charac‐
       ters  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  dig‐
       its  is	more  than  DECIMAL_DIG but the source value is exactly repre‐
       sentable 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 neg‐
       ative 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 char‐
	      acter 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 lan‐
       guage-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 simi‐
       lar to the one at the beginning of the output for  the  following  com‐
       mand:

	      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  get‐
       grgid();	 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 infor‐
       mation and, using the tm structure for values, places the date and time
       information into datestring. The printf() function  then	 outputs  dat‐
       estring 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	 pass‐
       word 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  ele‐
       ments 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 pre‐
       vious 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 .

IEEE/The Open Group		     2003			    FPRINTF(P)
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