In Linux, is there a way to align text on a delimiter?

Question

I have a script that basically runs tmux ls:

session1: 3 windows (created Fri Sep 20 13:16:13 2013) [157x56]
stuff: 3 windows (created Fri Sep 20 13:25:21 2013) [157x56]
asdf: 2 windows (created Sun Sep 29 23:06:33 2013) [77x17] (attached)
website: 1 windows (created Tue Sep 24 17:22:14 2013) [157x26]

I want the output of this script to be aligned at the colon, for readability. I know to use column -t but it doesn't quite do what I want (note the double spacing, and that the colons aren't actually aligned):

session1:  3  windows  (created  Fri  Sep  20  13:16:13  2013)  [157x56]
stuff:     3  windows  (created  Fri  Sep  20  13:25:21  2013)  [157x56]
asdf:      2  windows  (created  Sun  Sep  29  23:06:33  2013)  [77x17]   (attached)
website:   1  windows  (created  Tue  Sep  24  17:22:14  2013)  [157x26]

Here's the output I really want:

session1 : 3 windows (created Fri Sep 20 13:16:13 2013) [157x56]
stuff    : 3 windows (created Fri Sep 20 13:25:21 2013) [157x56]
asdf     : 2 windows (created Sun Sep 29 23:06:33 2013) [77x17] (attached)
website  : 1 windows (created Tue Sep 24 17:22:14 2013) [157x26]

What's the easiest/best way to achieve this in the Linux shell?

---

Edit: If you want to test your answer, you can use curl -s nylen.tv/tmux.txt instead of tmux ls.

Answer 1

With GNU sed you can specify the occurrence of the match so where s/ +/ /g would single space the whole file s/ +/ /2g single spaces the whole file but after the second match on each line:

$ column -t file | sed -re 's/: ( +)/\1: /' -e 's/ +/ /2g'
session1 : 3 windows (created Fri Sep 20 13:16:13 2013) [157x56]
stuff    : 3 windows (created Fri Sep 20 13:25:21 2013) [157x56]
asdf     : 2 windows (created Sun Sep 29 23:06:33 2013) [77x17] (attached)
website  : 1 windows (created Tue Sep 24 17:22:14 2013) [157x26]

To sort out the first columns spacing we use s/: ( +)/\1: / to match all the spaces from the : and we store n-1 spaces in the first capture group. We then replace the : and all the spaces with n-1 spaces followed by a : followed by a space (making n total space again).

Answer 2

How about this?

cat tmux.txt | sed 's/:/ : /' | column -t -o' ' | sed 's/ \+/ /2g' 
session1 : 3 windows (created Fri Sep 20 13:16:13 2013) [157x56]
stuff    : 3 windows (created Fri Sep 20 13:25:21 2013) [157x56]
asdf     : 2 windows (created Sun Sep 29 23:06:33 2013) [77x17] (attached)
website  : 1 windows (created Tue Sep 24 17:22:14 2013) [157x26]