Shell Programming and Scripting

Although the .99 will work for most fields, the standards say that -k1.5,1.99n specifies a sort key performing a numeric sort on the 5th through the 99th characters of the 1st field. The standard way to specify performing a numeric sort starting with the 5th character of the 1st field through the end of the 1st field would be -k1.5,1n or -k1.5,1.0n. And, for the record, the sort key -k1.5n specifies a numeric sort key starting with the 5th character of the 1st field and continuing through the end of the line.

Yes, 99 was a hack for as many digits as sort can find. Since sort probably does an atof(), it stops when it hits non-numeric after white space and then numeric.

Remember that in not -n, sort deals with letters -- you could go hex or just 0-9A-Z on a digit. As long as $LC_ALL is C, sort is in ascii/iso8859-1 one byte char land where 0-9 are less than A-Z. I even came up with a special code where I fused the values of visual synonyms like 0 and O, S and 5, 1 and I, 2 and Z, 8 and B together for a 5 bit number, but now I am 1 short, so choose a font with a small top on the 8 (10 + 26 = 36, - 4 = 32). I was working on tape identity numbers, where the OS had 5 places but the customer had way over 100K volumes. 5 5 bit numbers is 32 billion. If you go lower case an symbols, you might make 6 bits, again eliminating the visually similar.