awk CSV Split with headers Windows - csv

Question

Ok I have a csv file I need to split based on a column value which is fine, but I cannot get the headers to print in each file.
Currently I use:
awk "FS =\",\" {output=$3\".csv\"; print $0 > output}" test.csv
Which splits the files file based on column 3, but I don't know how to add the header to each file.
I've searched high & low but can't find a solution that will work in a one liner...
UPDATE
OK to date we have a working one liner:
awk -F, "NR==1{hdr=$0;next}!($3 in files){files[$3]=1;print hdr>$3\".csv\"}{print>$3\".csv\"}" test.csv
Or in test.awk:
BEGIN{FS=","} NR==1 {hdr=$0;next}!($3 in files) {files[$3]=1;print hdr>$3".csv"}{print>$3".csv"}
Command to run used:
awk -f test.awk test.csv
I really appreciate the help here, I've been trying for hours and have a few things left to work out.
1) Blank line inserted after header
2) Sort the data on specified fields
Further down the line I want to additionally do a row count & cut a reference number from another file is this possible with AWK or am I using the wrong tool for the job?
Thanks again.

Answer 1

UPDATED#2
Blank line after header line
UPDATED
Try this:
On Unix/cygwin (I tested on cygwin):
awk -F, 'NR==1{hdr=$0;next}!($3 in files){files[$3]=1;print hdr"\n">$3".csv"}{print>$3".csv"}' test.csv
Or adding Kent's ideas:
awk -F, 'NR==1{hdr=$0;next}{out=$3".csv"}!($3 in files){files[$3];print hdr"\n">out}{print>out}' test.csv
On windows cmd (not tested):
awk -F, "NR==1{hdr=$0;next}!($3 in files){files[$3]=1;print hdr\"\n\">$3\".csv\"}{print>$3\".csv\"}" test.csv
This stores the header line in test.csv to hdr. For the next lines it checks if the file name value is already exists. If not then stores its name in the files hash and prints the header line. And anyway it prints the whole line to the file.
Example file:
$ cat test.csv
A,B,C,D
1,2,a,3
4,5,b,4
Output
$ cat a.csv
A,B,C,D
1,2,a,3
$ cat b.csv
A,B,C,D
4,5,b,4
ADDED
If You would like to put the awk script into a file You could try (I cannot test is, sorry).
test.awk
BEGIN{FS=","}
NR==1 {hdr=$0;next}
!($3 in files) {files[$3]=1;print hdr"\n">$3".csv"}
{print>"$3.csv"}
Then You may call it as
awk -f test.awk test.csv

Answer 2

awk -F, 'NR==1{h=$0;next}{out=$3".csv";
if!(out in a)print h> out; print $0 > out;a[out]}' test.csv

Answer 3

Try something like this:
awk -F, '
BEGIN {
getline header
}
{
out=$3".csv"
if (!($3 in seen)) {
print header > out
}
print $0 > out
seen[$3]
}' test.csv
Windows version: (Not tested)
awk " FS =\",\"
BEGIN {
getline header
}
{
out=$3\".csv\"
if (!($3 in seen)) {
print header > out
}
print $0 > out
seen[$3]
}" test.csv

Answer 4

awk '{ output=$3".csv"; if( !($0 in a)) print "header" > output; a[$0]
print > output}' FS=, test.csv