how to check the size of a file in linux c

1If you have the file stream (FILE * f):
2
3fseek(f, 0, SEEK_END); // seek to end of file
4size = ftell(f); // get current file pointer
5fseek(f, 0, SEEK_SET); // seek back to beginning of file
6// proceed with allocating memory and reading the file
7
8Or,
9
10#include <sys/types.h>
11#include <sys/stat.h>
12#include <unistd.h>
13fd = fileno(f); 
14struct stat buf;
15fstat(fd, &buf);
16int size = buf.st_size;
17
18Or, use stat, if you know the filename:
19
20#include <sys/stat.h>
21struct stat st;
22stat(filename, &st);
23size = st.st_size;