ファイルから1行読み込み，読み込んだ文字数を返す関数

#include <stdio.h>

#define BUFFER_SIZE 64

int readln( char* s, int lim, FILE* fp ){

   int c, i = 0;
   
   while ( --lim > 0 && ( c = fgetc( fp ) ) != EOF && c != '\n' )
       s[ i++ ] = c;
   if ( c == '\n' )
       s[ i++ ] = c;
   s[ i ] = '\0';
   return i;
}

int main(){

    int c;
    char line[ BUFFER_SIZE ], *p, *pos;
    FILE *fp;

    fp = fopen( "input.dat", "r" );
    if ( fp != NULL ){
       while ( ( c = readln( line, BUFFER_SIZE, fp ) ) != 0 )
           printf( line );
       fclose( fp );
    }

    return 0;

}