Problem with sort command

[Justin White]

I have been using the sort command for years with a syntax as follows:

cat $file | sort -t, +1

I create filesystems on Linux and AIX from a CSV file and sort by the second
column as shown above.

Recently I have tried this command on RHEL 5.1 and it fails.  So I went and
tried on Ubuntu 9.04 and also fails.

Is this a bug or has the syntax for this type of sorting by columns changed?

ubuntu 9.04 and RHEL 5.1 command:

cat a.csv
1,3,3,4
1,9,3,4
1,2,3,4

$ cat a.csv | sort -t, +1
sort: open failed: +1: No such file or directory

RHEL 4:

# cat a.csv
1,3,3,4
1,9,3,4
1,2,3,4

# cat a.csv | sort -t, +1
1,2,3,4
1,3,3,4
1,9,3,4

# cat /etc/redhat-release
Red Hat Enterprise Linux ES release 4 (Nahant Update 5)

Thanks for any help you can provide.

Justin