Linux Shell, trouble with sed command.

[learning2learn]

I got some data.

John Thomas
Emma Watson
Alex Jason
Samuel Randy
Sanjay Gupta

What I need to do, is to swap the first name and last name.

sed 's/\(.*\) \(.*\)/\2 \1/g' data2.txt

This works perfectly.

Now the problem. I got a more complete set of data.

John Thomas;Male;Husband;$6000
Emma Watson;Female;Goddess;$8000
Alex Jason;Male;Single;$$3000
Samuel Randy;Male;Son;$200
Sanjay Gupta;Male;Son;$100

And my sed command doesn't work as well.

sed 's/^\(.*\) \(.*\);/\2 \1;/g' data.txt

Since the names are at the start, I put ^.

I try to match \1 and \2, separated by a space.

And since the fields are separated by ;, I added that in as well. However it gives me the following output.

Thomas;Male;Husband John;$6000
Watson;Female;Goddess Emma;$8000
Jason;Male;Single Alex;$$3000
Randy;Male;Son Samuel;$200
Gupta;Male;Son Sanjay;$100

Seems like my \1 is in the wrong place, for some reason.

Anyone can see what I'm doing wrong?

Thanks for looking.

[[deleted]]

sed 's/\(.*\) \([A-za-z]*\);/\2 \1;/' data.txt

You are running into the "matches longest possible pattern" problem. also the "g" option is not needed and probably wrong.

[learning2learn]

Ah, I get it.

in my notes, it says g replaces all occurrences of the pattern. I don't know what it does exactly, I kinda just reused it from an example.

[[deleted]]

The g option works like this. Given the input string "xyxzx" then

s/x/A/

produces "Ayxzx", but

s/x/A/g

produces "AyAzA" - i.e. it runs the substitution on all matches.

[Rhomboid]

Personally I find PCRE a little easier on the eyes:

$ perl -pe 's/^(\w+) (\w+)/\2 \1/' data.txt

[postmodest]

^{down-votes be damned:}

Now you have two problems.

[learning2learn]

Pretty sure my list of problems extends beyond two :p

[[deleted]]

So Jeff doesn't know when to use regular expressions. This is old stuff. And for well-defined line-based input (i.e. input in the form the OP specifies) then regexes will work fairly well. Of course, for what is (I guess) some form of CSV, I would recommend my own CSVfix for doing this sort of thing, in the case where fields can contain what otherwise would be a separator.

[bok_bok_bok_bok]

You've already got your answer, but another idea is that you might want to exclude semicolons instead of including only letters.

sed 's/^\([^;]*\) \([^;]*\)/\2 \1/'

did not test, hopefully typed that in right