fscanf() — Read Formatted Data

Format

#include <stdio.h>
int fscanf (FILE *stream, const char *format-string, argument-list);

Language Level

ANSI

Threadsafe

Yes

Locale Sensitive

The behavior of this function might be affected by the LC_CTYPE and LC_NUMERIC categories of the current locale. The behavior might also be affected by the LC_UNI_CTYPE category of the current locale if LOCALETYPE(*LOCALEUCS2) or LOCALETYPE(*LOCALEUTF) is specified on the compilation command. For more information, see Understanding CCSIDs and Locales.

Description

The fscanf() function reads data from the current position of the specified stream into the locations that are given by the entries in argument-list, if any. Each entry in argument-list must be a pointer to a variable with a type that corresponds to a type specifier in format-string.

The format-string controls the interpretation of the input fields and has the same form and function as the format-string argument for the scanf() function.

Return Value

The fscanf() function returns the number of fields that it successfully converted and assigned. The return value does not include fields that the fscanf() function read but did not assign.

The return value is EOF if an input failure occurs before any conversion, or the number of input items assigned if successful.

Example

This example opens the file myfile for reading and then scans this file for a string, a long integer value, a character, and a floating-point value.

#include <stdio.h>
 
#define  MAX_LEN  80
 
int main(void)
{
   FILE *stream;
   long l;
   float fp;
   char s[MAX_LEN + 1];
   char c;
 
   stream = fopen("mylib/myfile", "r");
 
   /* Put in various data. */
 
   fscanf(stream, "%s", &s [0]);
   fscanf(stream, "%ld", &l);
   fscanf(stream, "%c", &c);
   fscanf(stream, "%f", &fp);
 
   printf("string = %s\n", s);
   printf("long double = %ld\n", l);
   printf("char = %c\n", c);
   printf("float = %f\n", fp);
}
 
/***************  If myfile contains  ************************
**************** abcdefghijklmnopqrstuvwxyz 343.2 ***********
**********************  expected output is:  *********************
 
string = abcdefghijklmnopqrstuvwxyz
long double = 343
char = .
float = 2.000000
*/