C. How to get the file size

Open the file with fopen and point the file pointer to the end of the file.
Use ftell to get the current position of the file pointer (that is, the file length ).

Source code:
# Include "stdafx. H"
# Include <stdio. h>
# Include <iostream>

Using namespace STD;

Int main ()
{
File * fp = NULL;
Int nfilelen = 0;

Fp = fopen ("C:/test.txt", "rb ");

If (FP = NULL)
{
Cout <"can't open file" <Endl;
Return 0;
}

Fseek (FP, 0, seek_end); // locate the end Of the file
Nfilelen = ftell (FP); // file length

Cout <"file Len =" <nfilelen <Endl;
Return 0;
}

You can use the stat (WIN _ Stat) function to obtain the file size directly.
MAN 2 stat

1. Methods in MFC: (C ++)

Cfilestatus status;
Cfile: getstatus ("D: \ test.txt", status );
Long lsizeoffile;
Lsizeoffile = status. m_size;

The value of lsizeoffile is the size of the D: \ test.txt file.

2. Five methods for getting the file size from standard C
(Note: "_ file _" refers to the current file. You can change it to a target file in a valid path, such as "D: \ test.txt ")
Struct stat {
Dev_t st_dev;/* ID of device containing file */
Ino_t st_ino;/* inode Number */
Mode_t st_mode;/* Protection */
Nlink_t st_nlink;/* Number of hard links */
Uid_t st_uid;/* User ID of owner */
Gid_t st_gid;/* Group ID of owner */
Dev_t st_rdev;/* device ID (if special file )*/
Off_t st_size;/* Total size, in bytes */
Blksize_t st_blksize;/* blocksize for filesystem I/O */
Blkcnt_t st_blocks;/* number of blocks allocated */
Time_t st_atime;/* time of last access */
Time_t st_mtime;/* time of last modification */
Time_t st_ctime;/* time of last status change */
}

# Include "stdafx. H"
# Include "stdio. H"
# Include <sys/STAT. h>
# Include <Io. h>
# Include <fcntl. h>

Int getfilesize ()
{
Int iresult;
Struct _ stat Buf;
Iresult = _ Stat (_ file __, & BUF );
If (iresult = 0)
{
Return Buf. st_size;
}
Return NULL;
}

Int getfilesize01 ()
{
Int FP;
Fp = _ open (_ file __, _ o_rdonly );
If (FP =-1)
Return NULL;
Return _ filelength (FP );
// Return NULL;
}

Int getfilesize02 ()
{
Int FP;
Fp = _ open (_ file __, _ o_rdonly );
If (FP =-1)
Return NULL;
Return _ lseek (FP, 0, seek_end );
// Return NULL;
}

Int getfilesize03 ()
{
Int FP;
Fp = _ open (_ file __, _ o_rdonly );
If (FP =-1)
Return NULL;
Return _ lseek (FP, 0, seek_end );
// Return NULL;
}

Int getfilesize04 ()
{
File * FP;
If (FP = fopen (_ file __, "R") = NULL)
Return 0;
Fseek (FP, 0, seek_end );
Return ftell (FP); // return NULL;
}

Int getfilesize05 ()
{
File * FP;
Char STR [1];
If (FP = fopen (_ file __, "rb") = NULL)
Return 0;
For (INT I = 0 ;! Feof (FP); I ++)
{
Fread (& STR, 1, 1, FP );
}
Return I-1; // return NULL;
}

Int main (INT argc, char * argv [])
{
Printf ("getfilesize () = % d \ n", getfilesize ());
Printf ("getfilesize01 () = % d \ n", getfilesize01 ());
Printf ("getfilesize02 () = % d \ n", getfilesize02 ());
Printf ("getfilesize03 () = % d \ n", getfilesize03 ());
Printf ("getfilesize04 () = % d \ n", getfilesize04 ());
Printf ("getfilesize05 () = % d \ n", getfilesize05 ());
Return 0;
}