Concatenation of AWK array variables - unexpected behaviour

Question

Input file

steve,apples
steve,oranges
john,pears
john,oranges
mary,bananas
steve,plums
mary,nactarines

I want to get output like this:

steve:apples,oranges,plums
john:pears,oranges
mary:bananas,nectarines

Here is the one liner I have been trying to get to work:

awk -F, '{if(a[$1])a[$1]=a[$1]","$2; else a[$1]=$2;}END{for (i in a)print i ":" a[i];}' OFS=, inputfile

The output it gives is

,orangesrs
,plumsesples
,nactariness

It would appear that the string concatenation a[$1]=a[$1]","$2 is resulting in the original value of the array element to be overwritten to some degree. How can I carry out this concatenation correctly?

Incidentally, I get the same results on Centos, and Mac OSX.

That's strange. The file I had was one given to me by a customer, thart I then modified/simplified to show this proof of concept. I just recreated the file from scratch, and hey presto, it works... so I wonder why that original file didn't work! — Santrix
– Santrix, Commented Jun 26, 2014 at 14:52
Arrrghhh! The file was from a Windows machine - it was the extra CR that was causing stuff to get overwritten. Lesson learnt! — Santrix
– Santrix, Commented Jun 26, 2014 at 14:59

Jotne · Accepted Answer · 2014-06-26 20:36:59Z

2

You can try this:

awk -F, '{a[$1]=(a[$1]?a[$1]FS$2:$2)} END {for (i in a) print i":"a[i]}' file
mary:bananas,nactarines
john:pears,oranges
steve:apples,oranges,plums

PS After posted it, I see that this is the same as Kent posted, but no info on why deleted.

edited Jun 26, 2014 at 20:36

answered Jun 26, 2014 at 17:00

Jotne

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1 Comment

Jotne Over a year ago

@EdMorton I do forgetting :)

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