What is vscanf in C?

Parameters

The vscanf_s function takes in 2 mandatory arguments:

format: The pointer to the format string that may include format specifiers like %s.
arglist: A variable list of arguments of type va_list. This data type is defined in the stdarg.h header file.

An object of type va_list needs to be initialized by the va_start macro and needs to be released after use through the va_end macro

Return value

vscanf can return one of the two things:

Upon successful execution, it returns the number of items filled in the list of variable arguments given in the parameters.
If there is a failure during the assignment of arguments or while interpreting an input, or EOF (End Of File) is returned.

Example

The following is an example where we take a value as input followed by its unit and display it on stdout differently. For this example, we constructed a different function, get_store, that handles initializing and storage of the arglist. An example of the required input would be “500 Meters”:

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#include <stdio.h>
#include <stdarg.h>
// function to automatically initialize the list of arguments
void get_store ( const char * format, ... )
{
  // the arglist holds list of all arguments fed to this function
  va_list arglist;
  // initializing the arglish using the vs_start macro
  va_start (arglist, format);
  // putting the arguments into the arglist using vscanf
  vscanf (format, arglist);
  // releasing the arglish variable using the va_end macro 
  va_end (arglist);
}
int main ()
{
  // variables to store data into
  int magnitude;
  char unit[40];
  // sending format string and arguments to the get_store function 
  // this format string requires an input with first an integer folllowed by a string
  get_store (" %d %s ", &magnitude, unit);
  
  //printing out the variables to check data in it
  printf ("magnitude: %d\nunit: %s\n", magnitude, unit);
  return 0;
}

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What is vscanf in C?

Syntax

Parameters

Return value

Example