vsprintf()

Write formatted output to a buffer (varargs)

Synopsis:

#include <stdio.h>
#include <stdarg.h>

int vsprintf( char* buf,
              const char* format,
              va_list arg );

Arguments:

buf: A pointer to the buffer where you want to function to store the formatted string.
format: A string that specifies the format of the output. The formatting string determines what additional arguments you need to provide. For more information, see printf().
arg: A variable-argument list of the additional arguments, which you must have initialized with the va_start() macro.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The vsprintf() function formats data under control of the format control string, and writes the result to buf.

The vsprintf() function is a “varargs” version of sprintf().

Returns:

The number of characters written, or a negative value if an output error occurred (errno is set).

Examples:

Use vsprintf() in a general error message routine:

#include <stdio.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>

char msgbuf[80];

char *fmtmsg( char *format, ... )
  {
    va_list arglist;

    va_start( arglist, format );
    strcpy( msgbuf, "Error: " );
    vsprintf( &msgbuf[7], format, arglist );
    va_end( arglist );
    return( msgbuf );
  }

int main( void )
  {
    char *msg;

    msg = fmtmsg( "%s %d %s", "Failed", 100, "times" );
    printf( "%s\n", msg );
    return EXIT_SUCCESS;
  }

Classification:

ANSI, POSIX 1003.1

Safety:
Cancellation point	No
Interrupt handler	No
Signal handler	Read the Caveats
Thread	Yes

Caveats:

It's safe to call vsprintf() in a signal handler if the data isn't floating point.