系统环境变量还是挺重要的，除了QStandardPaths（感觉都是文档类型的变量，QT4使用QDesktopServices），更有QProcessEnvironment（都是真正的系统变量）:
QString strWindows = QProcessEnvironment::systemEnvironment().value("windir");
qDebug() << strWindows;
qDebug() << QProcessEnvironment::systemEnvironment().value("ALLUSERSPROFILE");
QStringList environmentList = QProcess::systemEnvironment();
foreach (QString environment, environmentList )
{
qDebug() << environment;
}
结果如下：
"ALLUSERSPROFILE=C:\ProgramData"
"APPDATA=C:\Users\kk\AppData\Roaming"
"CommonProgramFiles=C:\Program Files (x86)\Common Files"
"CommonProgramFiles(x86)=C:\Program Files (x86)\Common Files"
"CommonProgramW6432=C:\Program Files\Common Files"
"COMPUTERNAME=My-PC2"
"ComSpec=C:\Windows\system32\cmd.exe"
"FP_NO_HOST_CHECK=NO"
"GIT_SSH=C:\Program Files\TortoiseGit\bin\TortoiseGitPlink.exe"
"HOME=C:\Users\kk"
"HOMEDRIVE=C:"
"HOMEPATH=\Users\kk"
"LOCALAPPDATA=C:\Users\kk\AppData\Local"
"LOGONSERVER=\\BURO"
"NUMBER_OF_PROCESSORS=4"
"OS=Windows_NT"
"PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC"
"PROCESSOR_ARCHITECTURE=x86"
"PROCESSOR_ARCHITEW6432=AMD64"
"PROCESSOR_IDENTIFIER=Intel64 Family 6 Model 60 Stepping 3, GenuineIntel"
"PROCESSOR_LEVEL=6"
"PROCESSOR_REVISION=3c03"
"ProgramData=C:\ProgramData"
"ProgramFiles=C:\Program Files (x86)"
"ProgramFiles(x86)=C:\Program Files (x86)"
"ProgramW6432=C:\Program Files"
"PSModulePath=C:\Windows\system32\WindowsPowerShell\v1.0\Modules\"
"PUBLIC=C:\Users\Public"
"QMAKESPEC=C:\Qt\Qt5.3.2_static\mkspecs\win32-g++"
"QTDIR=C:\Qt\Qt5.3.2\5.3\msvc2010_opengl"
"SESSIONNAME=Console"
"SVN_SSH=C:\Program Files\TortoiseGit\bin\TortoiseGitPlink.exe"
"SystemDrive=C:"
"SystemRoot=C:\Windows"
"TEMP=C:\Users\kk\AppData\Local\Temp"
"TMP=C:\Users\kk\AppData\Local\Temp"
"USERDNSDOMAIN=MYPUB.COM"
"USERDOMAIN=MYPUB"
"USERNAME=kk"
"USERPROFILE=C:\Users\kk"
"VBOX_MSI_INSTALL_PATH=C:\Program Files\Oracle\VirtualBox\"
"VisualStudioDir=C:\Users\kk\Documents\Visual Studio 2010"
"VS100COMNTOOLS=C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\Tools\"
"VS110COMNTOOLS=C:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\Tools\"
"VS80COMNTOOLS=C:\Program Files (x86)\Microsoft Visual Studio 8\Common7\Tools\"
"VS90COMNTOOLS=C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\Tools\"
"windir=C:\Windows"
"windows_tracing_flags=3"
"windows_tracing_logfile=C:\BVTBin\Tests\installpackage\csilogfile.log"
"__COMPAT_LAYER=ElevateCreateProcess"
"PATH=C:\Qt\Qt5.3.2\5.3\msvc2010_opengl\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Program Files\TortoiseGit\bin;C:\Program Files (x86)\Git\cmd;C:\Qt\Qt5.3.2_min\Tools\mingw482_32\bin;C:\Qt\Qt5.3.2_min\5.3\mingw482_32\bin;C:\Python27;C:\Perl\bin;c:\Perl;C:\Qt\Qt5.3.2_min\Tools\mingw482_32\bin;C:\Program Files (x86)\Microsoft Visual Studio 10.0\;C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\bin"
----------------------------------------------------------------------------------------------
"HUSHLOGIN=FALSE"
"XCURSOR_THEME=Oxygen_White"
"HOME=/root"
"SSH_AGENT_PID=889"
"LANGUAGE=en_US:en"
"PATH=/opt/Qt5.3.2/5.3/gcc_64/bin:/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
"DBUS_SESSION_BUS_ADDRESS=unix:abstract=/tmp/dbus-N7rEvzXkaj,guid=e7ababcf3b59962702f3053356372866"
"XDG_CURRENT_DESKTOP=KDE"
"GTK2_RC_FILES=/etc/gtk-2.0/gtkrc:/root/.gtkrc-2.0:/root/.kde/share/config/gtkrc-2.0"
"GTK_RC_FILES=/etc/gtk/gtkrc:/root/.gtkrc:/root/.kde/share/config/gtkrc"
"XDG_SESSION_ID=1"
"XDG_VTNR=1"
"XDG_DATA_DIRS=/usr/share:/usr/share:/usr/local/share"
"XAUTHORITY=/tmp/kde-root/xauth-0-_0"
"MAIL=/var/mail/root"
"QT_PLUGIN_PATH=/root/.kde/lib/kde4/plugins/:/usr/lib/kde4/plugins/"
"WINDOWPATH=1"
"SHLVL=1"
"KDE_SESSION_VERSION=4"
"LANG=en_US.UTF-8"
"SESSION_MANAGER=local/sl-pc2:@/tmp/.ICE-unix/954,unix/sl-pc2:/tmp/.ICE-unix/954"
"KDE_FULL_SESSION=true"
"XDG_SEAT=seat0"
"LD_LIBRARY_PATH=/opt/Qt5.3.2/5.3/gcc_64/lib:/usr/local/lib:/usr/lib/x86_64-linux-gnu/:/usr/lib:/lib:/lib64:/home/steph/chilkat-9.5.0-x86_64-linux-gcc/lib"
"TERM=linux"
"DISPLAY=:0"
"QTDIR=/opt/Qt5.3.2/5.3/gcc_64"
"GS_LIB=/root/.fonts"
"_=/usr/bin/startx"
"KDE_SESSION_UID=0"
"LOGNAME=root"
"USER=root"
"QT_IM_MODULE=compose"
"SSH_AUTH_SOCK=/tmp/ssh-zA5qPgs0l5Jt/agent.828"
"KDE_MULTIHEAD=false"
"SHELL=/bin/bash"
"PWD=/root"
"XDG_RUNTIME_DIR=/run/user/0"