Add Column to end of CSV file using 'awk' in BASH script

You may add a comma to OFS (Output Field Separator):

awk -F"," 'BEGIN { OFS = "," } {$6="2012-02-29 16:13:00"; print}' input.csv > output.csv

Output:

2012-02-29,01:00:00,Manhatten,New York,234,2012-02-29 16:13:00
2012-02-29,01:00:00,Manhatten,New York,843,2012-02-29 16:13:00
2012-02-29,01:00:00,Manhatten,New York,472,2012-02-29 16:13:00
2012-02-29,01:00:00,Manhatten,New York,516,2012-02-29 16:13:00

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EDIT to answer the comment of SirOracle:

From awk man page:

       -v var=val
       --assign var=val
              Assign the value val to the variable var, before execution of the program begins.  Such 
              variable values are available to the BEGIN block of an AWK program.

So assign your date to a shell variable and use it inside awk:

mydate=$(date)
awk -v d="$mydate" -F"," 'BEGIN { OFS = "," } {$6=d; print}' input.csv > output.csv

I'd do:

awk '{ printf("%s,2012-02-29 16:13:00\n", $0); }' input.csv > output.csv

This hard codes the value, but so does your code.

Or you can use sed:

sed 's/$/,2012-02-29 16:13:00/' input.csv > output.csv