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Top Forums UNIX for Advanced & Expert Users Help optimizing sort of large files Post 302925230 by DGPickett on Friday 14th of November 2014 05:11:07 PM
Old 11-14-2014
Well defragged disk helps, as sort is doing sequential passes merging data. As a pattern, sequential is the fastest, if the adjacent file pages are really adjacent disk pages.

If sort has a big RAM footprint, it can move out of place items farther on each pass, as each pass reads from all sorted input streams into RAM and the smallest <= last is written to the newest temp output.

Fast sort space is critical, too, more critical than fast swap, but both are nice.
 

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UNIQ(1) 						      General Commands Manual							   UNIQ(1)

NAME
uniq - report repeated lines in a file SYNOPSIS
uniq [ -udc [ +n ] [ -n ] ] [ input [ output ] ] DESCRIPTION
Uniq reads the input file comparing adjacent lines. In the normal case, the second and succeeding copies of repeated lines are removed; the remainder is written on the output file. Note that repeated lines must be adjacent in order to be found; see sort(1). If the -u flag is used, just the lines that are not repeated in the original file are output. The -d option specifies that one copy of just the repeated lines is to be written. The normal mode output is the union of the -u and -d mode outputs. The -c option supersedes -u and -d and generates an output report in default style but with each line preceded by a count of the number of times it occurred. The n arguments specify skipping an initial portion of each line in the comparison: -n The first n fields together with any blanks before each are ignored. A field is defined as a string of non-space, non-tab charac- ters separated by tabs and spaces from its neighbors. +n The first n characters are ignored. Fields are skipped before characters. SEE ALSO
sort(1), comm(1) 7th Edition April 29, 1985 UNIQ(1)
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