A is for Awk, which runs like a snail, and
B is for Biff, which reads all your mail.
C is for CC, as hackers recall, while
D is for DD, the command that does all.
E is for Emacs, which rebinds your keys, and
F is for Fsck, which rebuilds your trees.
G is for Grep, a clever detective, while
H is for Halt, which may seem defective.
I is for Indent, which rarely amuses, and
J is for Join, which nobody uses.
K is for Kill, which makes you the boss, while
L is for Lex, which is missing from DOS.
M is for More, from which Less was begot, and
N is for Nice, which it really is not.
O is for Od, which prints out things nice, while
P is for Passwd, which reads in strings twice.
Q is for Quota, a Berkeley-type fable, and
R is for Ranlib, for sorting ar [sic] table.
S is for Spell, which attempts to belittle, while
T is for True, which does very little.
U is for Uniq, which is used after Sort, and
V is for Vi, which is hard to abort.
W is for Whoami, which tells you your name, while
X is, well, X, of dubious fame.
Y is for Yes, which makes an impression, and
Z is for Zcat, which handles compression.
Source is here :