UNIX for Dummies Questions & Answers

cscyabl@comet:(develop)> more file
2:A2
2:A1
5:A2
5:A2
10:A1
cscyabl@comet:(develop)> sort -n -u file
2:A1
5:A2
10:A1
cscyabl@comet:(develop)> sort -u -n file
2:A1
5:A2
10:A1
cscyabl@comet:(develop)> sort -u file | sort -n
2:A1
2:A2
5:A2
10:A1
cscyabl@comet:(develop)> sort -n file | sort -u
10:A1
2:A1
2:A2
5:A2

  -u  Suppresses all but one in each set of equal lines (for example, lines
      whose sort keys match exactly).  Ignored characters such as leading
      tabs and spaces, and characters outside of sort keys are not considered
      in this type of comparison.

  -n  Sorts any initial numeric strings (including regular expressions con-
      sisting of optional spaces, optional dashes, and zero (0) or more
      digits with optional radix character and thousands separator, as
      defined by the current locale) by arithmetic value.  An empty digit
      string is treated as zero; leading zeros and signs on zeros do not
      affect ordering.  Only one period (.) can be used in numeric strings.
      All subsequent periods (.) and any character to the right of the period
      (.) will be ignored

  The -d, -f, -i, -n, and -r options override the default ordering rules.
  When ordering options appear independent of any key field specifications,
  the requested field ordering rules are applied globally to all sort keys.
  When attached to a specific key (see -k), the specified ordering options
  override all global ordering options for that key.  In the obsolescent
  forms, if one or more of these options follows a +fskip option, it affects
  only the key field specified by that preceding option.