How can I get a file's size in C? [duplicate]

Question

How can I find out the size of a file I opened with an application written in C ? I would like to know the size, because I want to put the content of the loaded file into a string, which I allocate using malloc(). Just writing malloc(10000*sizeof(char)); is IMHO a bad idea.

Answer 1

You need to seek to the end of the file and then ask for the position:

fseek(fp, 0L, SEEK_END); sz = ftell(fp); 

You can then seek back, e.g.:

fseek(fp, 0L, SEEK_SET); 

or (if seeking to go to the beginning)

rewind(fp); 

Answer 2

Using standard library:

Assuming that your implementation meaningfully supports SEEK_END:

fseek(f, 0, SEEK_END); // seek to end of file size = ftell(f); // get current file pointer fseek(f, 0, SEEK_SET); // seek back to beginning of file // proceed with allocating memory and reading the file 

Linux/POSIX:

You can use stat (if you know the filename), or fstat (if you have the file descriptor).

Here is an example for stat:

#include <sys/stat.h> struct stat st; stat(filename, &st); size = st.st_size; 

Win32:

You can use GetFileSize or GetFileSizeEx.