Question

So, given that I have some type of data structure like this within a segment of code:

struct apple {
    int type, color;
    Apple app;
};

// ... more code

I want to take the full struct definition (and any other struct definitions in the file) and compress them into one line (so the file product would look something like:

struct apple { int type, color; Apple app; };

).

This is part of a homework assignment. I just learned sed in lecture not a week or so ago, and I’m very unsure as to how to do something like this. As such, if you feel uncomfortable answering things outright, I would appreciate if you could point me in the right direction so that I can learn how to use this utility correctly.

I’m assuming that one could accomplish things with sed by detecting the struct definition, and then keep reading each line into a global buffer until a } is found (I’m assuming there are no unions or anything in the struct definition). There seems to be a lot of power in this program though, and I can’t find any great introductions to it.

Answer 1

I’d do something in the line of this:

$ sed -n '/struct/,/};/p' input | sed -e ':a;N;$!ba;s/\n//g'
struct apple {    int type, color;    Apple app;};

The construct /foo/,/bar/ selects all lines (inclusive) between patterns.

The N command appends a newline and the next line to current pattern space. Then the famous s/// command gets executed which replaces the newline character with nothing, i.e. join of lines.