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On my Mac I used bash a lot. For my environment settings I added /usr/bin and /usr/local/bin into $PATH as I normally did.
While I do know what /usr/bin and /usr/local/bin are about, I am curious which should go before another, by convention? And is there a specific reason for that?
Similar is for /usr/lib and /usr/local/lib -- hopefully the answer is the same or similar.
a bit more -- Just an extension of the original question, how would you order the following in $PATH following the convention and why?
/bin
/sbin
/usr/bin
/usr/sbin
/usr/local/bin
/usr/local/sbin
/opt/local/bin
/opt/local/sbin
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-- /usr/bin This is the primary directory for executable programs. Most programs executed by normal users which are not needed for booting or for repairing the system and which are not installed locally should be -- /usr/local/bin Binaries for programs local to the site.
In traditional Unix systems, /usr usually contains files that come with the system distribution, and the /usr/local tree is free for the local administrator to manage. The only really hard and fast rule is that Unix distributions should not touch /usr/local , except perhaps to create the basic directories within it.
/bin contains executable files that are part of the core operating system. These files need to be accessible before /usr gets mounted. (for instance, the mount command is in /bin/mount ). /usr/bin contains executable files that are not part of the core operating system.
/usr/bin is where binaries supplied by the OS go. /usr/local/bin is where user supplied binaries go. When you type the name of a command on the command line, the shell searches for said command in the paths contained in the $PATH environment variable in order. A common pattern is to have /usr/local/bin precede /usr/bin in $PATH. This allows you to install alternate versions of binaries and have them gracefully "override" the binaries provided by the OS. And OS updates won't clobber your user installed packages. This pattern is notably used in OSX by the popular Homebrew package manager tool.
For instance, at the time of this writing, OSX El Capitan supplies git version 2.5.4 (in /usr/bin). If you want a newer version, you can use Homebrew to install git version 2.7.0 (into /usr/local/bin). Since /usr/local/bin comes before /usr/bin in the $PATH environment variable, when you issue the command git in a shell, the newer Homebrew version will be used.
On fresh new Mac running OSX El Capitan (I happen to have one), the /etc/paths file contains the following:
/usr/local/bin
/usr/bin
/bin
/usr/sbin
/sbin
which produces the following $PATH environment variable:
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
which is compatible with homebrew. I recommend sticking with this OSX default. If you really want to include /usr/local/sbin (listed in your question above), I would put it just before /usr/sbin for similar reasons to above. As for /opt/local/bin and /opt/local/sbin, I haven't personally found the need to add them to the path but it seems they might go in a similar spot as their /usr/local analogs, since /opt traditionally contains user installed binaries.
Note: The same explanation applies to /usr/lib vs. /usr/local/lib.
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