practicing techie

After downloading and installing Java SE 7 update 6 I tried running “java -version” to verify that the JDK was installed properly. To my surprise, the command reported the previous version instead of update 6. I then tried troubleshooting the problem using:

pkgutil --verbose --files com.oracle.jdk7u6
installer -dumplog -verbose -pkg '/Volumes/JDK 7 Update 06/JDK 7 Update 06.pkg' -target /

but with no effect. Then, browsing through the previous Java 7 installation directory parent directories I noticed that with update 6 the installation path was actually

/Library/Java/JavaVirtualMachines/jdk1.7.0_06.jdk

instead of

/Library/Java/JavaVirtualMachines/1.7.0.jdk

as with the previous Java 7 update releases, so I was using the old absolute path in my “java -version” command.

Now, on Linux one of my first troubleshooting methods would’ve been to use the strace command, but for some reason this doesn’t come instinctively for me on Mac OS X. On the Mac the equivalent command is called dtruss and it would’ve revealed the new installation path immediately, as strace would’ve:

dtruss 'installer -dumplog -verbose -pkg /Volumes/JDK\ 7\ Update\ 06/JDK\ 7\ Update\ 06.pkg -target /'
...
kevent(0x3, 0x153C67788, 0x1) = 1 0
audit_session_self(0x7FB1EB9640E0, 0x7FB1EBBEB150, 0x78) = 6659 0
kevent(0x3, 0x153C67788, 0x1) = 1 0
lstat64("/Library/Java/JavaVirtualMachines/jdk1.7.0_06.jdk", 0x153C65860, 0x1) = -1 Err#2
stat64("/Library/Java/JavaVirtualMachines/jdk1.7.0_06.jdk", 0x153C668B8, 0x0) = -1 Err#2
getattrlist("/", 0x153C665A0, 0x153C66190) = 0 0
getattrlist("/Library/Internet Plug-Ins/JavaAppletPlugin.plugin", 0x153C665A0, 0x153C66190) = 0 0
...

So, when troubleshooting OS level problems, system call tracing is always your friend, irrespective of the operating system. This is a good case in point.