More Tools For Building Tools

I’m working on more bash completions. This time for some of the command line tools Apple provides for sysadmins.

I decided there had to be a way to get a list of the options from the man page for a tool. After all they are all in there.

So I built a command line piece by piece. As an example let’s get a list of the options (with some caveats) for the tool pkgbuild. We start with man pkgbuild | col -b , the col -b step takes out the special characters man uses to show bold on screen. Now find all lines containing -- with grep, I liked grep -e '--'. If you have a look at the output of that we are getting close.

Next I decided to use sed to do a find and replace for the option itself. After some playing around I ended up with sed -e 's#.*\(--[a-zA-Z-]*\).*$#\1#' An important note for young players, it did take some time and a few tries to get that substitution just right. Don’t be afraid and remember Google (and Stack Exchange) are your friends.

First, I should point out an old Unix hand’s trick. Most of the time you see sed substitution commands using / as the separator but sed can use anything but \ or newline – it uses the first character it sees after the ‘s’. I usually use # as it makes the \ used for special characters easier to spot and the string easier to read.

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