append following lines to 1st line, every 3 lines


 
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# 1  
append following lines to 1st line, every 3 lines

I have output like this:
Code:
USER_ID
12/31/69 19:00:00
12/31/69 19:00:00
USER_ID
12/31/69 19:00:00
12/31/69 19:00:00
USER_ID
12/31/69 19:00:00
12/31/69 19:00:00
USER_ID
12/31/69 19:00:00
12/31/69 19:00:00
...

where USER_ID is a unique user login followed by their login timestamp and logout timestamp. How can I append the login and logout timestamps to the end of the user_id line? It would look like this:
Code:
USER_ID 12/31/69 19:00:00 12/31/69 19:00:00

I've been experimenting with this from the sed one-liners:
Quote:
Originally Posted by http://sed.sourceforge.net/sed1line.txt
# if a line ends with a backslash, append the next line to it
sed -e :a -e '/\\$/N; s/\\\n//; ta'
using this:
Code:
sed -e :a -e '/:[0-9][0-9]$/N; s/[0-9][0-9]$\n//; ta'

but it's producing:
Code:
USER_ID
12/31/69 19:00:12/31/69 19:00:USER_ID
12/31/69 19:00:12/31/69 19:00:USER_ID
12/31/69 19:00:12/31/69 19:00:USER_ID
12/31/69 19:00:12/31/69 19:00:USER_ID

Can someone advise?
# 2  
Code:
$ paste - - - < infile
USER_ID 12/31/69 19:00:00       12/31/69 19:00:00
USER_ID 12/31/69 19:00:00       12/31/69 19:00:00
USER_ID 12/31/69 19:00:00       12/31/69 19:00:00
USER_ID 12/31/69 19:00:00       12/31/69 19:00:00
$

These 3 Users Gave Thanks to jayan_jay For This Post:
# 3  
Quote:
Originally Posted by MaindotC
I've been experimenting with this from the sed one-liners:
using this:
Code:
sed -e :a -e '/:[0-9][0-9]$/N; s/[0-9][0-9]$\n//; ta'

but it's producing
This is easy to explain:

Code:
/:[0-9][0-9]$/N

This is saying apply the command (which is "N") to all lines of the form: a ":" followed by two digits at lines end. "N" combines a line with the following one, so it is easy to see, why your lines start with the dates and not the user-id.

What you want is to search for the user-id lines and then combine this with the next two lines. User-id lines are the ones without a date/time at the end, therefore we negate your search ("!" is a logical NOT):

Code:
/:[0-9][0-9]$/! {...}

Now lets see what we have to do with such a line: get the next two lines into our pattern space, then remove the newlines to combine the lines to one:

Code:
/:[0-9][0-9]$/! {N;N;s/\n//g;}

Now put that into a complete command:

Code:
sed '/:[0-9][0-9]$/! {N;N;s/\n/ /g;}' /path/to/input > path/to/output

Because your input file has a fixed structure (user-id, login timestamp on next line, logout timestamp on next) this will work and there is no need to take additional precautions, like in the oneliner example you found. It will fail, though, when this structure is disrupted.

I hope this helps.

bakunin
These 2 Users Gave Thanks to bakunin For This Post:
# 4  
Quote:
Originally Posted by jayan_jay
Code:
$ paste - - - < infile
USER_ID 12/31/69 19:00:00       12/31/69 19:00:00
USER_ID 12/31/69 19:00:00       12/31/69 19:00:00
USER_ID 12/31/69 19:00:00       12/31/69 19:00:00
USER_ID 12/31/69 19:00:00       12/31/69 19:00:00
$

Thanks, jay. I was unaware of the paste command. I was man -k "append" but if I had used the keyword "merge" I would have found it. I'm still dissecting bakunin's explanation.
# 5  
Just another sed statement if your whole file is formatted the same way than in your example :

Code:
sed 'N;N;s/\n/ /g' yourfile

These 2 Users Gave Thanks to ctsgnb For This Post:
# 6  
Quote:
Originally Posted by ctsgnb
Just another sed statement if your whole file is formatted the same way than in your example :

Code:
sed 'N;N;s/\n/ /g' yourfile

This one's even better because it doesn't add the extra-large space (perhaps a tab?) before the last set. Either way I have to read up on this "N" business in sed.
# 7  
You can also specify a delimiter (here, a space) with the paste alternative (to avoid the tabs that are used by default):

Code:
paste -d" " - - - <yourfile

 

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