Unix sort with scientific notation and two columns

Question

I'm scratching my head about the results of sorting two columns with unix sort.

Here's some dummy data in a file called test:

A       2e-12
A       3e-14
A       1e-15
A       1.2e-13
B       1e-13
B       1e-14
C       4e-12
C       3e-12

I would like to sort by column 1 first, then column 2, to produce:

A       1e-15
A       3e-14
A       1.2e-13
A       2e-12
B       1e-14
B       1e-13
C       3e-12
C       4e-12

If I give it just the second column to sort on, it will sort the scientific notation correctly:

sort -g -k2 test
A       1e-15
B       1e-14
A       3e-14
B       1e-13
A       1.2e-13
A       2e-12
C       3e-12
C       4e-12

This stack question addresses a similar problem, but it seems that my test only breaks down when I ask for two columns to sort on.

This other example looks really close to what I want, but when I give separate -k it doesn't alter the behavior for my test set.

These trials:

sort -k1,1 -g  test
sort -k1,1 -g -k1,2  test
sort -k1,1 -g -k2,1  test

Produce:

A       1.2e-13
A       1e-15
A       2e-12
A       3e-14
B       1e-13
B       1e-14
C       3e-12
C       4e-12

And these trials:

sort -g -k2 -k1  test
sort -g -k2 -k1,1  test
sort -g -k2,2 -k1,1  test
sort -k1,1 -g -k2,2 test
sort -k1,1 -g -k2,2  test

Produce:

A       1e-15
B       1e-14
A       3e-14
B       1e-13
A       1.2e-13
A       2e-12
C       3e-12
C       4e-12

I have tested with LANG=C and LC_ALL=C without luck. I'm running this on Red Hat and the version is GNU coreutils 8.22.

Answer 1

I figured it out while writing the stack question, so I thought I'd just go ahead and post the question with my solution.

I was confused about what the -kn,n meant and actually using sort with the --debug flag helped me find the answer.

This question pretty much nails it on the head: always use -kX,X to make sure I'm only considering one field at a time, and then specify g in the numeric field.

sort -k1,1 -k2,2g test
A       1e-15
A       3e-14
A       1.2e-13
A       2e-12
B       1e-14
B       1e-13
C       3e-12
C       4e-12

Yay!