When using file to check some file types, I noticed that it seems to incorrectly label C++ files as C files:
$ file User.*
User.cpp: C source, ASCII text
User.h: C++ source, ASCII text
User.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped
Why is it correctly identifying the header file, but not the cpp file?
From man page of file command,
file command actually performs 3 tests on determining the file type.
The filesystem tests are based on examining the return from a stat(2) system call.
The magic number tests are used to check for files with data in particular fixed formats.
The language tests look for particular strings (cf names.h) that can appear anywhere in the first few blocks of a file. For example, the keyword .br indicates that the file is most likely a troff(1) input file, just as the keyword struct indicates a C program.
The output of the file command is generally based on the result of any of the tests that succeeds.
Now, assuming the C++ program starts like this, and the third test succeeds,
#include <iostream.h>
bla
bla
As per the third test the keyword #include particularly specifies it is of type C program though we have a CPP program in hand. Now, when I check,
$ file example.cpp
example.cpp: ASCII C program text
Now, the concepts of object oriented are specific to C++. Let us create a file specific to C++.
I start my C++ program as,
Class something
{
}
bla
bla
Now, when I issue
$ file example.cpp
The output is,
example.cpp: ASCII C++ program text
