Member Avatar for seemant_sun

write a program to find size of a file without traversing it character by character?

will anybody tell me the logic hw to approach it

is there any trick involved

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  • Latest Post Latest Post by Ancient Dragon

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Short answer: you do not need to read a file byte‑by‑byte. There are two common approaches: seek to the end of a stream (fast, simple for binary files) or ask the filesystem for the file’s metadata (portable and reliable for byte counts).

’s fseek/ftell approach works if you open the file in binary mode; when C I/O performs newline or encoding translations in text mode the position returned can be implementation‑defined, so it may not equal the byte count (see fopen and ftell). Contrary to , there is no literal “EOF” byte at the end of a file — EOF is an I/O condition reported by functions, not a stored character (see EOF).

’s stat idea is the usual POSIX method: stat/fstat provide st_size (logical file size in bytes) — that is the recommended way on Unix-like systems (see stat). ’s warning about huge files is valid: older APIs and the long return of ftell can overflow on 32‑bit builds. Use the 64‑bit variants or compile with large‑file support (or use platform APIs) for files >2 GB (see large‑file support and GetFileSizeEx on Windows).

Extra gotchas: st_size is the logical byte count — sparse files, filesystem compression or network mounts can make disk usage differ from that number (sparse files). If the goal is “number of characters” in human text, bytes != characters for multibyte encodings (you must decode to count characters).

Recommended: for C on POSIX, use stat/fstat to get bytes and enable 64‑bit file support for large files. On Windows, use the Win32 size APIs. For C++ programs, std::filesystem::file_size wraps the platform calls safely. See links below for details:

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Member Avatar for ArkM

Use fseek and ftell functions from <stdio.h>.

Member Avatar for csurfer

Every file ends with an EOF character.Find out what the functions which ArkM has stated does and use the above information and you are done.

Member Avatar for jephthah

are you using *nix?

#include <stdio.h>
#include <sys/stat.h>

int getFileSize(char *filename, long *filesize)
{
   struct stat filestats;              

   if (stat(filename, &filestats) < 0) {
   { 
      perror(filename);
      return 0; 
   } 
   else
      *filesize = filestats.st_size;

   printf(" The size of %s is %ld bytes (%3.1f KB)\n", filename, *filesize, (*filesize / 1024.0) );
   return 1;
}

.

Member Avatar for Ancient Dragon

Those C functions may not work with huge files -- files that are larger than 2 gig. In MS-Windows win32 api functions would be needed to get the file size of huge files. I don't know about *nix or MAC

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