How can I determine the OS within .bash_profile?

Question

On my main machine, a MacBook Pro, I have a .bash_profile file that I'd like to use unaltered on my Dreamhost linux machine. However, there's a few lines that are only applicable to macOS, such as alias mvim="/Applications/MacVim.app/Contents/MacOS/MacVim".

Is there a way in bash to test for whether it's running under macOS or Debian (or just not macOS) and only execute that above line, and a few others, when running under macOS? Whereas other questions here address how to find out which Linux distro is being used, here I only need to know if I'm running on macOS or Linux, and the solutions for knowing the Linux distro aren't available on macOS.

Answer 1

On OSX, uname -s returns Darwin (most Linux uname programs return Linux).

As a general rule (aside from personal use), uname has quirks for different systems. In autoconf, scripts use config.guess, which provides consistent information.

For example in my Debian 7,

x86_64-pc-linux-gnu

and in OSX El Capitan

x86_64-apple-darwin15.5.0

You could use if-then-else statements in the shell, or a case-statement. The latter are more easily maintained, e.g.,

case $(config.guess) in
*linux*)
    DoSomeLinuxStuff
    ;;
*apple-darwin*)
    DoSomeMacStuff
    ;;
esac

Many Linux distributions add information to the output of uname, but this is useful only on a case-by-case basis. There is no standard for the information added.

For my Debian 7:

$ uname -v
#1 SMP Debian 3.2.81-1

while OSX is radically different:

$ uname -v
Darwin Kernel Version 15.5.0: Tue Apr 19 18:36:36 PDT 2016; root:xnu-3248.50.21~8/RELEASE_X86_64

Further reading:

• config.guess

Answer 2

if [[ $(uname -s) == Linux ]]
then
    doThis
else
    doThat
fi

Answer 3

As an alternate solution, you might try splitting your .bash_profile into a portable part and a system-specific part.

In your main .bash_profile add the following:

if [ -f ~/.bash_profile_local ] ; then
    . ~/.bash_profile_local
fi

Then put any customizations that apply only to a given system into .bash_profile_local on that system. If you have no customizations, you don't have to create the file.

Or, if you wanted to go even further and have pieces shared among some systems but not others, you could do a full-on SYSV-style rc.d directory. In .bash_profile:

if [ -d ~/.bash_profile.d ] ; then
    for f in ~/.bash_profile.d/* ; do
        if [ -f "$f" ] ; then
            . "$f"
        fi
    done
fi

Then create a .bash_profile.d directory, and any files you put in there will be run as if they were part of your .bash_profile.