Hi I have two csv files having same columns like,
x.csv
column1,column2
A,2
B,1
y.csv
column1,column2
A,1
C,2
I want the output like:
z.csv
column1,column2
A,2
B,1
C,2
i.e. for the matching data in first column, I want to keep the x.csv record and for a new field in y.csv (like A,2) i just want to append it (like C,2).
Thanks
$ awk -F, 'NR==FNR{a[$1]; print; next} ! ($1 in a)' x.csv y.csv
column1,column2
A,2
B,1
C,2
-F,
This tells awk to use a comma as the field separator
NR==FNR{a[$1]; print; next}
While reading the first file (NR==FNR), this tells awk to (a) to add $1 as a key to the associative array a, (b) print the line, and (c) skip the remaining commands and jump to the next line in a file.
! ($1 in a)
If we get here, that means we are working on the second file. In that case, we print the line if the first field is not a key of array a (in other words, if the first field did not appear in the first file).
next statement really neccessary since the ! ($1 in a) will never match the first file?=1.