Q: sort csv file using unix utililty sort is there a way to sort very large CSV file using sort?
Simply sort by the first column, however, the data might contain line breaks within a column (standard CSV file rules apply).  Would the line breaks break the sort utility?

A: I believe you should try something like this cat old.csv | sort > new.csv 
UPD: To prepare data if needed we can use AWK script....

A: The sort function will sort the lines in asciicographical order.  To get a more sophisticated effect, you might use the UNIX utility awk.

A: You could do it with a mix of utilities. Hopefully I've understood it correctly ... and if so, this might do the job. IF not, point out where I've gone wrong in an assumption :-) This requires that the number of fields per CSV record is fixed (it's also a dirt simple example that doesn't cover various CSV variations (e.g., hello,"world,how",are,you would break as "world,how" would be split into two fields)):
hello,world,how,are,you
one,two,three,four,five
once,I,caught,a
fish,alive
hey,now,hey,now,now

And this awk script:
BEGIN {
        FS=","
        fields=0
}

{
        if (line == "") {
                fields=NF
                line = $0
        } else {
                fields=fields + (NF - 1)
                line=line"|"$0
        }
}

fields == 5 {
        print line
        fields = 0
        line = ""
}

Executing this:
awk -f join.awk < infile | sort | tr '|' '\n'

gives this output:
hello,world,how,are,you
hey,now,hey,now,now
once,I,caught,a
fish,alive
one,two,three,four,five

In essence, all we're doing with the awk script is merging the multi-line records into a single-line that we can then feed to sort, then break again with tr. I'm using a pipe as the replacement for the newline char -- just choose something that you can gurantee will not appear in a CSV record.
Now it might not be perfect for what you want, but hopefully it'll nudge you in the right direction. The main thing with the awk script I've knocked up is that it needs to know how many fields there are per CSV record. This needs to be fixed. If it's variable, then all bets are off as there'd need to be more rules in there do define the semantic nature of the file that you want to sort...

A: A simpler approach is to temporarily modify your data so that the standard UNIX sort command can properly interpret your data.
You can use a program called csvquote which replaces the problematic commas and newlines inside quoted field values with nonprinting characters. Then it restores those characters at the end of your pipeline.
For example,
csvquote inputfile.csv | sort | csvquote -u

You can find the code here: https://github.com/dbro/csvquote
