Default file extension of the executable created by g++ under Cygwin vs Linux.

Question

Hi All,

I've done most of my work on VisualStudio and don't have much experience with gcc or g++. When I tried to compile a (ex. aprogram.cpp) this morning on my pc using cygwin, I got (aprogram.exe) when I tried to compile the same thing on my Ubuntu box I got (aprogram) w/o any extension. I am just wondering if someone be kind enough to tell me why. This question is just out of curiosity. :)

Thanks in advance!

EDIT: (from Jimmy's comment) g++ under Cygwin defaults to .exe

Answer 1

.exe is a windows thing. Unix doesn't care about extensions. Executability is based on metadata on the file as well as the file's contents. g++ through cygwin is not really a windows app, so it carries its unix roots with it.

Answer 2

It's just a naming convention. On Unix/Linux, executables don't have an extension, just an executable bit.

Answer 3

That's easy: on UNIX, you don't need no steenkin' extensions. In fact, an "extension" like .c is just a convenient naming convention; unlike Windows, the file system sees the file name as one string, .c and all.

For a really good time, compile a C program with no -o flag at all. Your executable will still show up --- named the default name for executables: a.out.

Answer 4

If you were wondering how to execute the program on UNIX, simply navigate to the folder with your program you wish to execute (aprogram) and type

./aprogram

This will tell the shell you wish to execute 'aprogram' in the current directory.

Answer 5

If you want the output to have an .exe extension then just use the -o flag to do so (e.g. -o aprogram.exe). It will work just fine under linux either way.

The ability to execute a program under linux is based on the file's permissions (see chmod). Execute permissions will be automatically set by gcc/g++.

Answer 6

Executables have no extension in the unix world, because they are meant to be executed in the shell. Imagine the following:

cat.bin file.txt | less.bin

That's ugly! Unix makes use of so-called magic bytes at the start of each file to detect the file-type. For the default binary format, called ELF, there is a 4 byte word 7f 45 4c 46 at the start. That's not possible for all file formats. Consider C code or Java code. They can both start with comments, and can be made look exactly the same. So you still have to use file-name extensions, and it's a good thing when used where it's appropriate.

Answer 7

ls /bin There are lot's of programs and all of them without extension :)

ls -l /bin you will see that all of them has +x flag to mark them as an executable.