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To get OS and VER, the latest standard seems to be /etc/os-release. Before that, there was lsb_release and /etc/lsb-release. Before that, you had to look for different files for each distribution.

Here's what I'd suggest

if [ -f /etc/os-release ]; then
    # freedesktop.org and systemd
    . /etc/os-release
    OS=$NAME
    VER=$VERSION_ID
elif type lsb_release >/dev/null 2>&1; then
    # linuxbase.org
    OS=$(lsb_release -si)
    VER=$(lsb_release -sr)
elif [ -f /etc/lsb-release ]; then
    # For some versions of Ubuntu without lsb_release command
    . /etc/lsb-release
    OS=$DISTRIB_ID
    VER=$DISTRIB_RELEASE
elif [ -f /etc/debian_version ]; then
    # Older Debian/Ubuntu/etc.
    OS=Debian
    VER=$(cat /etc/debian_version)
elif [ -f /etc/SuSe-release ]; then
    # Older SuSE/etc.
    ...
elif [ -f /etc/redhat-release ]; then
    # Older Red Hat, CentOS, etc.
    ...
else
    # Fall back to uname, e.g. "Linux <version>", also works for BSD, etc.
    OS=$(uname -s)
    VER=$(uname -r)
fi

I think uname to get ARCH is still the best way. But the example you gave obviously only handles Intel systems. I'd either call it BITS like this:

case $(uname -m) in
x86_64)
    BITS=64
    ;;
i*86)
    BITS=32
    ;;
*)
    BITS=?
    ;;
esac

Or change ARCH to be the more common, yet unambiguous versions: x86 and x64 or similar:

case $(uname -m) in
x86_64)
    ARCH=x64  # or AMD64 or Intel64 or whatever
    ;;
i*86)
    ARCH=x86  # or IA32 or Intel32 or whatever
    ;;
*)
    # leave ARCH as-is
    ;;
esac

but of course that's up to you.

To get OS and VER, the latest standard seems to be /etc/os-release. Before that, there was lsb_release and /etc/lsb-release. Before that, you had to look for different files for each distribution.

Here's what I'd suggest

if [ -f /etc/os-release ]; then
    # freedesktop.org and systemd
    . /etc/os-release
    OS=$NAME
    VER=$VERSION_ID
elif type lsb_release >/dev/null 2>&1; then
    # linuxbase.org
    OS=$(lsb_release -si)
    VER=$(lsb_release -sr)
elif [ -f /etc/lsb-release ]; then
    # For some versions of Debian/Ubuntu without lsb_release command
    . /etc/lsb-release
    OS=$DISTRIB_ID
    VER=$DISTRIB_RELEASE
elif [ -f /etc/debian_version ]; then
    # Older Debian/Ubuntu/etc.
    OS=Debian
    VER=$(cat /etc/debian_version)
elif [ -f /etc/SuSe-release ]; then
    # Older SuSE/etc.
    ...
elif [ -f /etc/redhat-release ]; then
    # Older Red Hat, CentOS, etc.
    ...
else
    # Fall back to uname, e.g. "Linux <version>", also works for BSD, etc.
    OS=$(uname -s)
    VER=$(uname -r)
fi

I think uname to get ARCH is still the best way. But the example you gave obviously only handles Intel systems. I'd either call it BITS like this:

case $(uname -m) in
x86_64)
    BITS=64
    ;;
i*86)
    BITS=32
    ;;
*)
    BITS=?
    ;;
esac

Or change ARCH to be the more common, yet unambiguous versions: x86 and x64 or similar:

case $(uname -m) in
x86_64)
    ARCH=x64  # or AMD64 or Intel64 or whatever
    ;;
i*86)
    ARCH=x86  # or IA32 or Intel32 or whatever
    ;;
*)
    # leave ARCH as-is
    ;;
esac

but of course that's up to you.

Most recent distributions have lsb_release, or at least /etc/lsb-release, which you can use to get OS and VER.

I think uname to get ARCH is still the best way.

e.g.

OS=$(lsb_release -si)
ARCH=$(uname -m | sed 's/x86_//;s/i[3-6]86/32/')
VER=$(lsb_release -sr)

or

. /etc/lsb-release
OS=$DISTRIB_ID
ARCH=$(uname -m | sed 's/x86_//;s/i[3-6]86/32/')
VER=$DISTRIB_RELEASE

If you have to be compatible with older distributions, there is no single file you can rely on. Either fall back to the output from uname, e.g.

OS=$(uname -s)
ARCH=$(uname -m)
VER=$(uname -r)

or handle each distribution separately:

if [ -f /etc/debian_version ]; then
    OS=Debian
    VER=$(cat /etc/debian_version)
elif [ -f /etc/redhat-release ]; then
    # TODO add code for Red Hat and CentOS here

It's probably best to combine all this:

ARCH=$(uname -m | sed 's/x86_//;s/i[3-6]86/32/')

if type lsb_release >/dev/null 2>&1; then
    OS=$(lsb_release -si)
    VER=$(lsb_release -sr)
elif [ -f /etc/lsb-release ]; then
    . /etc/lsb-release
    OS=$DISTRIB_ID
    VER=$DISTRIB_RELEASE
elif [ -f /etc/debian_version ]; then
    OS=Debian
    VER=$(cat /etc/debian_version)
elif [ -f /etc/redhat-release ]; then
    # TODO add code for Red Hat and CentOS here
    ...
else
    OS=$(uname -s)
    VER=$(uname -r)
fi

Finally, your ARCH obviously only handles Intel systems. I'd either call it BITS like this:

To get OS and VER, the latest standard seems to be /etc/os-release. Before that, there was lsb_release and /etc/lsb-release. Before that, you had to look for different files for each distribution.

Here's what I'd suggest

if [ -f /etc/os-release ]; then
    # freedesktop.org and systemd
    . /etc/os-release
    OS=$NAME
    VER=$VERSION_ID
elif type lsb_release >/dev/null 2>&1; then
    # linuxbase.org
    OS=$(lsb_release -si)
    VER=$(lsb_release -sr)
elif [ -f /etc/lsb-release ]; then
    # For some versions of Ubuntu without lsb_release command
    . /etc/lsb-release
    OS=$DISTRIB_ID
    VER=$DISTRIB_RELEASE
elif [ -f /etc/debian_version ]; then
    # Older Debian/Ubuntu/etc.
    OS=Debian
    VER=$(cat /etc/debian_version)
elif [ -f /etc/SuSe-release ]; then
    # Older SuSE/etc.
    ...
elif [ -f /etc/redhat-release ]; then
    # Older Red Hat, CentOS, etc.
    ...
else
    # Fall back to uname, e.g. "Linux <version>", also works for BSD, etc.
    OS=$(uname -s)
    VER=$(uname -r)
fi

I think uname to get ARCH is still the best way. But the example you gave obviously only handles Intel systems. I'd either call it BITS like this:

ARCH=$(uname -m | sed 's/x86_//;s/i[3-6]86/32/')

if [ -f /etc/lsb-release ]; then
    . /etc/lsb-release
    OS=$DISTRIB_ID
    VER=$DISTRIB_RELEASE
elif [ -f /etc/debian_version ]; then
    OS=Debian
    VER=$(cat /etc/debian_version)
elif [ -f /etc/redhat-release ]; then
    # TODO add code for Red Hat and CentOS here
    ...
else
    OS=$(uname -s)
    VER=$(uname -r)
fi

ARCH=$(uname -m | sed 's/x86_//;s/i[3-6]86/32/')

if type lsb_release >/dev/null 2>&1; then
    OS=$(lsb_release -si)
    VER=$(lsb_release -sr)
elif [ -f /etc/lsb-release ]; then
    . /etc/lsb-release
    OS=$DISTRIB_ID
    VER=$DISTRIB_RELEASE
elif [ -f /etc/debian_version ]; then
    OS=Debian
    VER=$(cat /etc/debian_version)
elif [ -f /etc/redhat-release ]; then
    # TODO add code for Red Hat and CentOS here
    ...
else
    OS=$(uname -s)
    VER=$(uname -r)
fi