sort - sort a file of ASCII lines
sort [-bcdfimnru] [-tc] [-o name] [+pos1] [-pos2] file ...
-b Skip leading blanks when making comparisons
-c Check to see if a file is sorted
-d Dictionary order: ignore punctuation
-f Fold upper case onto lower case
-i Ignore nonASCII characters
-m Merge presorted files
-n Numeric sort order
-o Next argument is output file
-r Reverse the sort order
-t Following character is field separator
-u Unique mode (delete duplicate lines)
sort -nr file # Sort keys numerically, reversed
sort +2 -4 file # Sort using fields 2 and 3 as key
sort +2 -t: -o out # Field separator is :
sort +.3 -.6 # Characters 3 through 5 form the key
Sort sorts one or more files. If no files are specified, stdin is
sorted. Output is written on standard output, unless -o is specified.
The options +pos1 -pos2 use only fields pos1 up to but not including pos2
as the sort key, where a field is a string of characters delimited by
spaces and tabs, unless a different field delimiter is specified with -t.
Both pos1 and pos2 have the form m.n where m tells the number of fields
and n tells the number of characters. Either m or n may be omitted.
comm(1), grep(1), uniq(1).