How to detect the OS from a Bash script?

Question

I think the following should work. I'm not sure about win32 though.

if [[ "$OSTYPE" == "linux-gnu"* ]]; then
        # ...
elif [[ "$OSTYPE" == "darwin"* ]]; then
        # Mac OSX
elif [[ "$OSTYPE" == "cygwin" ]]; then
        # POSIX compatibility layer and Linux environment emulation for Windows
elif [[ "$OSTYPE" == "msys" ]]; then
        # Lightweight shell and GNU utilities compiled for Windows (part of MinGW)
elif [[ "$OSTYPE" == "win32" ]]; then
        # I'm not sure this can happen.
elif [[ "$OSTYPE" == "freebsd"* ]]; then
        # ...
else
        # Unknown.
fi

For my .bashrc, I use the following code:

platform='unknown'
unamestr=`uname`
if [[ "$unamestr" == 'Linux' ]]; then
   platform='linux'
elif [[ "$unamestr" == 'FreeBSD' ]]; then
   platform='freebsd'
fi

Then I do somethings like:

if [[ $platform == 'linux' ]]; then
   alias ls='ls --color=auto'
elif [[ $platform == 'freebsd' ]]; then
   alias ls='ls -G'
fi

It's ugly, but it works. You may use case instead of if if you prefer.

The bash manpage says that the variable OSTYPE stores the name of the operation system:

OSTYPE Automatically set to a string that describes the operating system on which bash is executing. The default is system- dependent.

It is set to linux-gnu here.

$OSTYPE

You can simply use pre-defined $OSTYPE variable e.g.:

case "$OSTYPE" in
  solaris*) echo "SOLARIS" ;;
  darwin*)  echo "OSX" ;; 
  linux*)   echo "LINUX" ;;
  bsd*)     echo "BSD" ;;
  msys*)    echo "WINDOWS" ;;
  cygwin*)  echo "ALSO WINDOWS" ;;
  *)        echo "unknown: $OSTYPE" ;;
esac

However it's not recognized by the older shells (such as Bourne shell).

---

uname

Another method is to detect platform based on uname command.

See the following script (ready to include in .bashrc):

# Detect the platform (similar to $OSTYPE)
OS="`uname`"
case $OS in
  'Linux')
    OS='Linux'
    alias ls='ls --color=auto'
    ;;
  'FreeBSD')
    OS='FreeBSD'
    alias ls='ls -G'
    ;;
  'WindowsNT')
    OS='Windows'
    ;;
  'Darwin') 
    OS='Mac'
    ;;
  'SunOS')
    OS='Solaris'
    ;;
  'AIX') ;;
  *) ;;
esac

You can find some practical example in my .bashrc.

---

Here is similar version used on Travis CI:

case $(uname | tr '[:upper:]' '[:lower:]') in
  linux*)
    export TRAVIS_OS_NAME=linux
    ;;
  darwin*)
    export TRAVIS_OS_NAME=osx
    ;;
  msys*)
    export TRAVIS_OS_NAME=windows
    ;;
  *)
    export TRAVIS_OS_NAME=notset
    ;;
esac