[bash] How to check if running in Cygwin, Mac or Linux?

I have a shell script that is used both on Windows/Cygwin and Mac and Linux. It needs slightly different variables for each versions.

How can a shell/bash script detect whether it is running in Cygwin, on a Mac or in Linux?

Bash sets the shell variable OSTYPE. From man bash:

Automatically set to a string that describes the operating system on which bash is executing.

This has a tiny advantage over uname in that it doesn't require launching a new process, so will be quicker to execute.

However, I'm unable to find an authoritative list of expected values. For me on Ubuntu 14.04 it is set to 'linux-gnu'. I've scraped the web for some other values. Hence:

case "$OSTYPE" in
  linux*)   echo "Linux / WSL" ;;
  darwin*)  echo "Mac OS" ;; 
  win*)     echo "Windows" ;;
  msys*)    echo "MSYS / MinGW / Git Bash" ;;
  cygwin*)  echo "Cygwin" ;;
  bsd*)     echo "BSD" ;;
  solaris*) echo "Solaris" ;;
  *)        echo "unknown: $OSTYPE" ;;
esac

The asterisks are important in some instances - for example OSX appends an OS version number after the 'darwin'. The 'win' value is actually 'win32', I'm told - maybe there is a 'win64'?

Perhaps we could work together to populate a table of verified values here:

• Linux Ubuntu (incl. WSL): linux-gnu
• Cygwin 64-bit: cygwin
• Msys/MINGW (Git Bash for Windows): msys

(Please append your value if it differs from existing entries)

http://en.wikipedia.org/wiki/Uname

All the info you'll ever need. Google is your friend.

Use uname -s to query the system name.

• Mac: Darwin
• Cygwin: CYGWIN_...
• Linux: various, LINUX for most

Here is the bash script I used to detect three different OS type (GNU/Linux, Mac OS X, Windows NT)

Pay attention

• In your bash script, use #!/usr/bin/env bash instead of #!/bin/sh to prevent the problem caused by /bin/sh linked to different default shell in different platforms, or there will be error like unexpected operator, that's what happened on my computer (Ubuntu 64 bits 12.04).
• Mac OS X 10.6.8 (Snow Leopard) do not have expr program unless you install it, so I just use uname.

Design

1. Use uname to get the system information (-s parameter).
2. Use expr and substr to deal with the string.
3. Use if elif fi to do the matching job.
4. You can add more system support if you want, just follow the uname -s specification.

Implementation

#!/usr/bin/env bash

if [ "$(uname)" == "Darwin" ]; then
    # Do something under Mac OS X platform        
elif [ "$(expr substr $(uname -s) 1 5)" == "Linux" ]; then
    # Do something under GNU/Linux platform
elif [ "$(expr substr $(uname -s) 1 10)" == "MINGW32_NT" ]; then
    # Do something under 32 bits Windows NT platform
elif [ "$(expr substr $(uname -s) 1 10)" == "MINGW64_NT" ]; then
    # Do something under 64 bits Windows NT platform
fi

Testing

• Linux (Ubuntu 12.04 LTS, Kernel 3.2.0) tested OK.
• OS X (10.6.8 Snow Leopard) tested OK.
• Windows (Windows 7 64 bit) tested OK.

What I learned

1. Check for both opening and closing quotes.
2. Check for missing parentheses and braces {}

References

• [1] uname - wikipedia
• [2] shell script syntax error: unexpected end of file
• [3] Detect the OS from a Bash script
• [4] BASH Programming Introduction HOW-TO

Use only this from command line works very fine, thanks to Justin:

#!/bin/bash

################################################## #########
# Bash script to find which OS
################################################## #########

OS=`uname`
echo "$OS"

source

Windows Subsystem for Linux did not exist when this question was asked. It gave these results in my test:

uname -s -> Linux
uname -o -> GNU/Linux
uname -r -> 4.4.0-17763-Microsoft

This means that you need uname -r to distinguish it from native Linux.

Ok, here is my way.

osis()
{
    local n=0
    if [[ "$1" = "-n" ]]; then n=1;shift; fi

    # echo $OS|grep $1 -i >/dev/null
    uname -s |grep -i "$1" >/dev/null

    return $(( $n ^ $? ))
}

e.g.

osis Darwin &&
{
    log_debug Detect mac osx
}
osis Linux &&
{
    log_debug Detect linux
}
osis -n Cygwin &&
{
    log_debug Not Cygwin
}

I use this in my dotfiles

To build upon Albert's answer, I like to use $COMSPEC for detecting Windows:

#!/bin/bash

if [ "$(uname)" == "Darwin" ]
then
 echo Do something under Mac OS X platform
elif [ "$(expr substr $(uname -s) 1 5)" == "Linux" ]
then
  echo Do something under Linux platform
elif [ -n "$COMSPEC" -a -x "$COMSPEC" ]
then 
  echo $0: this script does not support Windows \:\(
fi

This avoids parsing variants of Windows names for $OS, and parsing variants of uname like MINGW, Cygwin, etc.

Background: %COMSPEC% is a Windows environmental variable specifying the full path to the command processor (aka the Windows shell). The value of this variable is typically %SystemRoot%\system32\cmd.exe, which typically evaluates to C:\Windows\system32\cmd.exe .

I guess the uname answer is unbeatable, mainly in terms of cleanliness.

Although it takes a ridiculous time to execute, I found that testing for specific files presence also gives me good and quicker results, since I'm not invoking an executable:

So,

[ -f /usr/bin/cygwin1.dll ] && echo Yep, Cygwin running

just uses a quick Bash file presence check. As I'm on Windows right now, I can't tell you any specific files for Linuxes and Mac OS X from my head, but I'm pretty sure they do exist. :-)

Use uname -s (--kernel-name) because uname -o (--operating-system) is not supported on some Operating Systems such as Mac OS and Solaris. You may also use just uname without any argument since the default argument is -s (--kernel-name).

The below snippet does not require bash (i.e. does not require #!/bin/bash)

#!/bin/sh

case "$(uname -s)" in

   Darwin)
     echo 'Mac OS X'
     ;;

   Linux)
     echo 'Linux'
     ;;

   CYGWIN*|MINGW32*|MSYS*|MINGW*)
     echo 'MS Windows'
     ;;

   # Add here more strings to compare
   # See correspondence table at the bottom of this answer

   *)
     echo 'Other OS' 
     ;;
esac

The below Makefile is inspired from Git project (config.mak.uname).

ifdef MSVC     # Avoid the MingW/Cygwin sections
    uname_S := Windows
else                          # If uname not available => 'not' 
    uname_S := $(shell sh -c 'uname -s 2>/dev/null || echo not')
endif

# Avoid nesting "if .. else if .. else .. endif endif"
# because maintenance of matching if/else/endif is a pain

ifeq ($(uname_S),Windows)
    CC := cl 
endif
ifeq ($(uname_S),OSF1)
    CFLAGS += -D_OSF_SOURCE
endif
ifeq ($(uname_S),Linux)
    CFLAGS += -DNDEBUG
endif
ifeq ($(uname_S),GNU/kFreeBSD)
    CFLAGS += -D_BSD_ALLOC
endif
ifeq ($(uname_S),UnixWare)
    CFLAGS += -Wextra
endif
...

See also this complete answer about uname -s and Makefile.

The correspondence table in the bottom of this answer is from Wikipedia article about uname. Please contribute to keep it up-to-date (edit the answer or post a comment). You may also update the Wikipedia article and post a comment to notify me about your contribution ;-)

Operating System uname -s
Mac OS X Darwin
Cygwin 32-bit (Win-XP) CYGWIN_NT-5.1
Cygwin 32-bit (Win-7 32-bit)CYGWIN_NT-6.1
Cygwin 32-bit (Win-7 64-bit)CYGWIN_NT-6.1-WOW64
Cygwin 64-bit (Win-7 64-bit)CYGWIN_NT-6.1
MinGW (Windows 7 32-bit) MINGW32_NT-6.1
MinGW (Windows 10 64-bit) MINGW64_NT-10.0
Interix (Services for UNIX) Interix
MSYS MSYS_NT-6.1
MSYS2 MSYS_NT-10.0-17763
Windows Subsystem for Linux Linux
Android Linux
coreutils Linux
CentOS Linux
Fedora Linux
Gentoo Linux
Red Hat Linux Linux
Linux Mint Linux
openSUSE Linux
Ubuntu Linux
Unity Linux Linux
Manjaro Linux Linux
OpenWRT r40420 Linux
Debian (Linux) Linux
Debian (GNU Hurd) GNU
Debian (kFreeBSD) GNU/kFreeBSD
FreeBSD FreeBSD
NetBSD NetBSD
OpenBSD OpenBSD
DragonFlyBSD DragonFly
Haiku Haiku
NonStop NONSTOP_KERNEL
QNX QNX
ReliantUNIX ReliantUNIX-Y
SINIX SINIX-Y
Tru64 OSF1
Ultrix ULTRIX
IRIX 32 bits IRIX
IRIX 64 bits IRIX64
MINIX Minix
Solaris SunOS
UWIN (64-bit Windows 7) UWIN-W7
SYS$UNIX:SH on OpenVMS IS/WB
z/OS USS OS/390
Cray sn5176
(SCO) OpenServer SCO_SV
(SCO) System V SCO_SV
(SCO) UnixWare UnixWare
IBM AIX AIX
IBM i with QSH OS400
HP-UX HP-UX

# This script fragment emits Cygwin rulez under bash/cygwin
if [[ $(uname -s) == CYGWIN* ]];then
    echo Cygwin rulez
else 
    echo Unix is king
fi

If the 6 first chars of uname -s command is "CYGWIN", a cygwin system is assumed