unix sorting, with primary and secondary keys

Question

I would like to sort a file on more fields. A sample tab separated file is:

a   1   1.0
b   2   0.1
c   3   0.3
a   4   0.001
c   5   0.5
a   6   0.01
b   7          


        

Answer 1

The manual shows some examples.

In accordance with zseder's comment, this works:

sort -t"<TAB>" -k1,1d -k3,3g

Tab should theoretically work also like this sort -t"\t".

If none of the above work to delimit by tab, this is an ugly workaround:

TAB=`echo -e "\t"`
sort -t"$TAB"

Answer 2

Here is a Python script that you might use as a starting point:

#!/usr/bin/env python2.6

import sys
import string

def main():
    fname = sys.argv[1]
    data = []
    with open(fname, "rt") as stream:
        for line in stream:
            line = line.strip()
            a, b, c = line.split()
            data.append((a, int(b), float(c)))
    data.sort(key=my_key)
    print data


def my_key(item):
    a, b, c = item
    return c, lexicographical_key(a)


def lexicographical_key(a):
    # poor man's attempt, should use Unicode classification etc.
    return a.translate(None, string.punctuation)


if __name__ == "__main__":
    main()