= File line sort

        SORt  n[-[m]][/[b][c][d][i][r]]  [n[-[m]]...] [NX] [NB] [.lab1 .lab2]
        SORt  [/o]{N|T|S}[-]

            2nd format is to sort dirlist.
            If Bounds is set move the margin only.

            -n[-[m]] is sort key,up to 5 keys allowed.
               n    : sort key start at colomn n and length is 1.
               n-   : sort key start at colomn n and length is 9,999.
               n-m  : sort key is from column n to column m.
            -follow option just after each key. ex) 10-20/r
               b    :check duplicated key line.
               c    :Case Sensitive.This is default.
               d    :check key break line.
               i    :Case Insensitive.
               r    :reverse sequence
            -NX     :Sort displayed lines(Not eXcluded) only.
            -NB     :Ignore Bounds setting(move whole line).
            -.lab1/2:Limit sort line range using a pair of label
                     on lineno column. line number may be used so as to
                     limit line range with no label on lineno column.

            -/ox[-] :x=N:nameSeq, x=T:timestampSeq, x=S:sizeSeq,
                     -:discending.