Install Xcode command line tools on 10.7.x - 10.10.x. Tested on 10.7.5, 10.8.5, 10.9.5 and 10.10.2.

install_xcode.sh

#!/bin/bash

# Installing the Xcode command line tools on 10.7.x or higher
osx_vers=$(sw_vers -productVersion | awk -F "." '{print $2}')
cmd_line_tools_temp_file="/tmp/.com.apple.dt.CommandLineTools.installondemand.in-progress"

# Installing the latest Xcode command line tools on 10.9.x or higher

if [[ "$osx_vers" -ge 9 ]]; then

    # Create the placeholder file which is checked by the softwareupdate tool
    # before allowing the installation of the Xcode command line tools.

    touch "$cmd_line_tools_temp_file"

    # Find the last listed update in the Software Update feed with "Command Line Tools" in the name

    cmd_line_tools=$(softwareupdate -l | awk '/\*\ Command Line Tools/ { $1=$1;print }' | tail -1 | sed 's/^[[ \t]]*//;s/[[ \t]]*$//;s/*//' | cut -c 2-)

    #Install the command line tools

    softwareupdate -i "$cmd_line_tools"

    # Remove the temp file

    if [[ -f "$cmd_line_tools_temp_file" ]]; then
      rm "$cmd_line_tools_temp_file"
    fi
fi

# Installing the latest Xcode command line tools on 10.7.x and 10.8.x

# on 10.7/10.8, instead of using the software update feed, the command line tools are downloaded
# instead from public download URLs, which can be found in the dvtdownloadableindex:
# https://devimages.apple.com.edgekey.net/downloads/xcode/simulators/index-3905972D-B609-49CE-8D06-51ADC78E07BC.dvtdownloadableindex

if [[ "$osx_vers" -eq 7 ]] || [[ "$osx_vers" -eq 8 ]]; then

    if [[ "$osx_vers" -eq 7 ]]; then
        DMGURL=http://devimages.apple.com/downloads/xcode/command_line_tools_for_xcode_os_x_lion_april_2013.dmg
    fi

    if [[ "$osx_vers" -eq 8 ]]; then
         DMGURL=http://devimages.apple.com/downloads/xcode/command_line_tools_for_osx_mountain_lion_april_2014.dmg
    fi

        TOOLS=cltools.dmg
        curl "$DMGURL" -o "$TOOLS"
        TMPMOUNT=`/usr/bin/mktemp -d /tmp/clitools.XXXX`
        hdiutil attach "$TOOLS" -mountpoint "$TMPMOUNT" -nobrowse
        # The "-allowUntrusted" flag has been added to the installer
        # command to accomodate for now-expired certificates used
        # to sign the downloaded command line tools.
        sudo installer -allowUntrusted -pkg "$(find $TMPMOUNT -name '*.mpkg')" -target /
        hdiutil detach "$TMPMOUNT"
        rm -rf "$TMPMOUNT"
        rm "$TOOLS"
fi

exit 0