2005/05/26 sort -g vs. sort -n
When sorting numbers, you can use either -g or -n. I've noticed that Linux users without Unix experience tend to use -g, while old Unix folk are often unaware of that flag at all and continue to use -n. There is a difference between the two flags, although "man sort" doesn't explain it - "info sort" does a better job.
For ordinary numbers, -g and -n are identical, and although -g is slower, for small input sets it really doesn't matter. But when you mix in scientific notation, -n does not work:
$ cat t 123 12 11 9 453 99 10e1 10e0 101 1 8.95 $ sort -n t 1 8.95 9 10e0 10e1 11 12 99 101 123 453 $ sort -g t 1 8.95 9 10e0 11 12 99 10e1 101 123 453
I mentioned that "sort -g" is slower. That's because it calls "strtod" to convert to double-precision floating point. When -n is used, sort simply aligns decimal points (real or assumed) and then does an ordinary string comparison. That's much faster, but of course it fails to handle scientific notation. The "faster" is, as noted, usually unimportant:
$ wc -l t 1321 t $ time sort -g t > /dev/null real 0m0.013s user 0m0.012s sys 0m0.002s $ time sort -n t > /dev/null real 0m0.009s user 0m0.008s sys 0m0.001s
You may have "-g" even if your man page doesn't mention it: my Mac OS X Tiger has -g but the man page doesn't mention it.`
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