How to specify gcc version at runtime? - unix

Question

Is it possible to have multiple gcc versions installed on a unix system? If yes, how to find which all versions are installed? Also, is it possible to specify at runtime which gcc version to use?

Answer 1

Here's a step by step that works on Linux, and will probably work on unix.
First verify you have a gcc available:
greg#greg-mint ~ $ gcc
gcc: fatal error: no input files
compilation terminated.
Yep. Didn't like the fact I didn't supply anything to compile.
If you get something like no command gcc found or command or file not recognised: gcc then you might have a problem.
Now, find where that gcc is:
greg#greg-mint ~ $ which gcc
/usr/bin/gcc
Great. It's in /usr/bin/gcc but that's not telling us about alternative versions.
Let's find out a bit about that:
greg#greg-mint ~ $ ls -l /usr/bin/gcc
lrwxrwxrwx 1 root root 7 Mar 28 2013 /usr/bin/gcc -> gcc-4.7
On my machine (Linux Mint) that' show it shows a symbolic link. What it means is that when I run the gcc command it's running /usr/bin/gcc-4.7
Ok. I'm guessing it's usually in /usr/bin, so, lets see if there are any others:
greg#greg-mint ~ $ ls -l /usr/bin/gcc*
lrwxrwxrwx 1 root root 7 Mar 28 2013 /usr/bin/gcc -> gcc-4.7
-rwxr-xr-x 1 root root 275952 Jul 3 2012 /usr/bin/gcc-4.5
-rwxr-xr-x 1 root root 578808 Sep 22 2012 /usr/bin/gcc-4.7
-rwxr-xr-x 1 root root 22832 Sep 22 2012 /usr/bin/gcc-ar-4.7
-rwxr-xr-x 1 root root 22832 Sep 22 2012 /usr/bin/gcc-nm-4.7
-rwxr-xr-x 1 root root 22832 Sep 22 2012 /usr/bin/gcc-ranlib-4.7
-rwxr-xr-x 1 root root 220968 Oct 9 2012 /usr/bin/gccxml
-rwxr-xr-x 1 root root 8606464 Oct 9 2012 /usr/bin/gccxml_cc1plus
So it turns out I have gcc version 4.7 and 4.5 on my machine. I don't know what the other ones are.
You can specify the version number by sending the full path:
greg#greg-mint ~ $ gcc --version
gcc (Ubuntu/Linaro 4.7.2-2ubuntu1) 4.7.2
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
greg#greg-mint ~ $ /usr/bin/gcc-4.5 --version
gcc-4.5 (Ubuntu/Linaro 4.5.4-1ubuntu2) 4.5.4
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
greg#greg-mint ~ $ /usr/bin/gcc-4.7 --version
gcc-4.7 (Ubuntu/Linaro 4.7.2-2ubuntu1) 4.7.2
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
An alternative, and I recommend that you DO NOT do this, is to use find. (be warned: on a shared machine it's not necessarily good manners).
find / -name "gcc*"
This will look for all files that start with gcc on your machine. It's going to scan the entire disk, so it will take a while, and you'll be affecting performance for all the other users on your system (which given you've said 'unix' and 'University Server' may come with an impact).

Answer 2

Yes, it is fairly common to have multiple versions of gcc installed, usually named gcc-version. For example, on my machine, I have gcc-4.4, gcc-4.5, and gcc-4.6. You can usually see what versions you have installed by typing gcc-tab -- using the shell's autocomplete to tell you which versions are available.