If I had a file that contained the following

test1
test2
test3
test4
test5
test6
test7
test8

and I wanted the end result to be

test1
test2 test3
test4
test5 test6
test7
test8

What would be the best method at accomplishing this?

I think you need to be a bit more detailed about your requirements. Do you only need to specify the line numbers to combine, or do you need to match certain text strings? Is it only concatenating sequential lines, or will you have a need to combine lines that are separated by something else?

Taking the opening post at face value, you can do this with sed:
Each expression '-e' will take the line number you specify, combine it with the following line and then replace the newline separating them with a space. You could easily change the line number to a text match if necessary by replacing the line number with /textstring/.

more specifics....

'Dave the H.' hit the nail on the head. I need it to match the string test2. When I try it with his string, the output is correct. However, when I change it to look for the actual text, it is erroring.

So I think that the search string might need to be a little different.

The whole point is to search for a string. If the string is found, append the entire line to the end of the previous line.

Sorry for being generic.

Look closer at what I wrote. You need to enclose the text in slashes '/test2/'. This turns it into a regular expression string, which will match if it appears anywhere in the line.

edit:

By the way, "If the string is found, append it to the end of the previous line" is a little more difficult than appending the following line to the one that matches. Which one do you really want?

Whatever would be the easiest I guess. I need to move lines around so that the end result would be a line looking like

The example works fine with /textstring/. But lest say the test2 was 'test2foofoofoofoo' and I only wanted to search for test2. Would I use a wildcard? /test2*/

The search will match partial strings. Add a dollar sign to the end of the text string if you don't want it to match a partial string. '/test2$/'

In regular expressions, ^=startofline and $=endofline, so if you wanted to match a whole line you'd need to use '/^test2$/'.

And no, * wouldn't work. Its regex meaning is slightly different from the familiar globbing wildcard. In regex it means "match the preceding character zero or more times". To simulate the * wildcard in regex, you'd have to use ".*", where the period means "any character".

(edit: actually, it looks like * alone does work in this case. I guess sed can handle it either way here.)

There are many good regex tutorials on the net. I recommend reading up on it.

Thanks 'David the H.'!! I will read up on some of that and see what I can find out.

I appreciate the help!!!

I don't know if you guys want to know, but this is how I got my file working...

sed '
/^host/ {
N
s/\n//
}' file.x > file.y

This did what I needed to do. Thanks for all of your help!

Glad to see you got it working. I notice two things to be cautious about though.

'/^host/' will match every line that starts with 'host', no matter what else follows.

's/\n//' will simply delete the line-break. The two lines will run together with no space between them.

I hope these are what you want.

BTW, you can now mark your threads as "solved", so that future readers will know you got a satisfactory answer. It's in the thread tools box. You may want to use it to mark this one.