libc.info: vprintf

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`vprintf', `vfprintf', `vsprintf'--format argument list

*Synopsis*
     #include <stdio.h>
     #include <stdarg.h>
     int vprintf(const char *FMT, va_list LIST);
     int vfprintf(FILE *FP, const char *FMT, va_list LIST);
     int vsprintf(char *STR, const char *FMT, va_list LIST);
     int vasprintf(char **STRP, const char *FMT, va_list LIST);
     int vsnprintf(char *STR, size_t SIZE, const char *FMT, va_list LIST);
     int _vprintf_r(void *REENT, const char *FMT,
         va_list LIST);
     int _vfprintf_r(void *REENT, FILE *FP, const char *FMT,
         va_list LIST);
     int _vasprintf_r(void *REENT, char **STR, const char *FMT,
         va_list LIST);
     int _vsprintf_r(void *REENT, char *STR, const char *FMT,
         va_list LIST);
     int _vsnprintf_r(void *REENT, char *STR, size_t SIZE, const char *FMT,
         va_list LIST);
   *Description*
`vprintf', `vfprintf', `vasprintf', `vsprintf' and `vsnprintf' are
(respectively) variants of `printf', `fprintf', `saprintf', `sprintf',
and `snprintf'.  They differ only in allowing their caller to pass the
variable argument list as a `va_list' object (initialized by `va_start')
rather than directly accepting a variable number of arguments.
*Returns*
The return values are consistent with the corresponding functions:
`vasprintf'/`vsprintf' returns the number of bytes in the output string,
save that the concluding `NULL' is not counted.  `vprintf' and
`vfprintf' return the number of characters transmitted.  If an error
occurs, `vprintf' and `vfprintf' return `EOF' and `vasprintf' returns
-1.  No error returns occur for `vsprintf'.
*Portability*
ANSI C requires all three functions.
   Supporting OS subroutines required: `close', `fstat', `isatty',
`lseek', `read', `sbrk', `write'.