~/.bash_profile在某些情况下没有执行
下面是解释
Opening a new terminal in X invokes bash as an interactive shell, but not as a login shell. Therefore your ~/.bash_profile will not execute, but your ~/.bashrc should.
.bash_profile is only supposed to be run once, by the login shell. .bashrc is the file that's run for each child.
意思是，只有是interactive login shell(交互式登录终端)的情况下，才会执行~/.bash_profile，~/.bash_profile会调用~/.bashrc，看~/.bash_profile内容即知。
如果不是interactive login shell，例如启动X终端，或者ssh自动登录，这相当于启动了一个登录终端的child，只会执行~/.bashrc。
实验验证：
我是用putty登录的，用了ssh，启动时执行了screen。
在~/.bash_profile末尾加上
echo bash_profile ran $(date)
在~/.bashrc末尾加上
echo bashrc ran $(date)
重新用putty登录，得到
.bashrc ran Wed Feb 27 09:34:40 CST 2013
看来，我登录的情况，只有~/.bashrc得到了执行。
更详细的解释，man bash 看INVOCATION 段。
