-r      reverse order (i.e. descending)
-f          fold lowercase into uppercase letters
-u      eliminate duplicate lines
-d      letters, digits, spaces only (ie. ignore punctuation chars)
-n      numerically  (else 10 < 9)
-k N     sort from the Nth field
+i       sort from the i+1th field.  obsolete
-i   sort to i+1th field
+i.j sort on i+1th field starting at j+1th position of that field
-tc      change field separator to c

-b  ignore leading blanks (fields start at first leading blank)
-o  output file (can be input file)

$ sort -r -n -t: -k3 /etc/passwd
# sort passwd file in reverse order, numerically by UID

$ sort -n -k2
#sort numerically on second field

$ sort -n +4 -5 +1 -2
#sort fourth field primary sort key, second field secondary key
$ sort -o combo a b c #merge previously sorted a b c files into combo file

extract columns or fields from a file. Vertical slices.

$ cut -c1-3,5-10 myfile
# columns 1,2,3,5,6,7,8,9,10 to output

-ffield-list default field separator is Tab
$ cut -f2,5 myfile
# fields 2 and 5 output

-dc change field separator to c
$ cut -f2 "-d " myfile
# space as field separator, output 2nd field

$ cut -f5 -d: /etc/passwd
# name field of password file

files together side by side
(cat concatenates files)