NAME

     snprintf, vsnprintf - formatted output conversion

SYNOPSIS

     #define _GNU_SOURCE
     #include <stdio.h>

     int snprintf ( char *str, size_t n,
                              const char *format, ... );

     #include <stdarg.h>

     int vsnprintf ( char *str, size_t n,
                              const char *format, va_list ap );

DESCRIPTION

     snprintf writes output to the string str, under  control  of
     the  format  string  that specifies how subsequent arguments
     are converted for output.   It  is  similar  to  sprintf(3),
     except  that n specifies the maximum number of characters to
     produce.  The trailing null  character  is  counted  towards
     this limit, so you should allocate at least n characters for
     the string str.

     vsnprintf is the equivalent of snprintf  with  the  variable
     argument list specified directly as for vprintf.

RETURN VALUE

     If the output was truncated, the return value is -1,  other-
     wise  it  is  the number of characters stored, not including
     the terminating null.

EXAMPLES

     Here is an example program which  dynamically  enlarges  its
     output buffer.

         /* Construct a message describing the value of a
            variable whose name is NAME and whose value is
            VALUE. */
         char *
         make_message (char *name, char *value)
         {
           /* Guess we need no more than 100 chars of space. */
           int size = 100;
           char *buffer = (char *) xmalloc (size);
           while (1)
             {
               /* Try to print in the allocated space. */
               int nchars = snprintf (buffer, size,
                             "value of %s is %s", name, value);
               /* If that worked, return the string. */
               if (nchars > -1)
                 return buffer;
               /* Else try again with twice as much space. */
               size *= 2;
               buffer = (char *) xrealloc (buffer, size);
             }
         }

CONFORMING TO

     These are GNU extensions.

SEE ALSO

     printf(3), sprintf(3), vsprintf(3),