Detecting and concatenating a multi-line structure using sed

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开发者_如何学运维 introductions to it.

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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.

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there may be better way to solve this problem, e.g. awk maybe with tr. However since you mentioned that this is homework, and must be done by sed, I wrote the below commands (one liner :D ). note, there are two "sed" command. hope it could be accepted.

command to solve the problem:

sed -rn '/^struct/{x;s/.*/#/g;x;p;n}; 
    /\};/ {x;/#/{s/#//;x;p;n}};
    x; /#/{x;p}' yourFile | sed -r ':a;N; s/\n//g;s/\};/&\n/g; ba;' 

now let's do a test, I created a file named t.c. see the content:

kent$  cat t.c
struct apple1 {
    int type, color;
    Apple app;
};

// ... more code
// ... more code
// ... more code
// ... more code
function abc(para){
 foo;
 bar;
 return ;
}
struct apple2 {
    int type, color;
    Apple app;
};

// ... more code
// ... more code
// ... more code 
struct apple3 {
    int type, color;
    Apple app;
};

// ... more code

now play my sed commands with the t.c baby:

kent$  sed -rn '/^struct/{x;s/.*/#/g;x;p;n}; 
        /\};/ {x;/#/{s/#//;x;p;n}};
        x; /#/{x;p}' t.c | sed -r ':a;N; s/\n//g;s/\};/&\n/g; ba;' 

struct apple1 {    int type, color;    Apple app;};
struct apple2 {    int type, color;    Apple app;};
struct apple3 {    int type, color;    Apple app;};