Fourth day-----file location function and buffer refresh function

/*
  Function: Set file offset location
Parameter 1:file Flow
  Parameter 2: Offset

  Parameter 3: Offset position: Seek_set, seek_cur,  seek_end
  Return value: Returns 0 successfully, otherwise returns 1 and sets errno
*/intlongint  whence);
/*
  Function: Determine the location of the file location pointer
  Parameter 1:file Flow
  return value: The current position of the file location pointer, otherwise return-1, and set errno*/ long ftell (FILE *stream); /*
  Function: File location pointer definition to file start location
  Parameter 1:file Flow
  return value: None
*/void Rewind (FILE *stream);

The program for determining file size using the Fseek function and the Ftell function:

#include <stdio.h>#include<stdlib.h>intMainintARGC,Char**argv) {FILE*FP; if(ARGC <2) {fprintf (stderr,"usage....\n"); Exit (1); } FP= fopen (argv[1],"R"); if(fp = =NULL) {Perror ("fopen ()"); Exit (1); } fseek (FP,0, Seek_end); printf ("%ld\n", Ftell (FP)); Exit (0);}

Using the fseek function to produce an empty file

/*  Function: Refreshes a stream
  Parameter 1:file stream, if null, refreshes all stream
  */ int fflush (FILE *stream);

Buffer function: Merging system calls

Line buffer: Refresh when line breaks, full time brush, Force refresh (stdout)

Full buffer: Full time brush, Force refresh (default, except stdout)

Unbuffered: Content that needs to be output immediately (stderr)

To set the buffering mode:

int Char int mode, size_t size);

Fourth day-----file location function and buffer refresh function