(08:36) Programs> dir
total 4
-rw------- 1 538 Sep 11 08:15 first.l
(08:36) Programs> dir
total 4
-rw------- 1 538 Sep 11 08:15 first.l
(08:37) Programs> flex first.l 
(08:37) Programs> dir
total 52
-rw------- 1   538 Sep 11 08:15 first.l
-rw-r--r-- 1 45478 Sep 11 08:37 lex.yy.c
(08:37) Programs> gcc lex.yy.c 
(08:37) Programs> dir
total 76
-rw------- 1   538 Sep 11 08:15 first.l
-rw-r--r-- 1 45478 Sep 11 08:37 lex.yy.c
-rwxr-xr-x 1 23592 Sep 11 08:37 a.out
(08:37) Programs> ./a.out 
a*(b-17) + 5/c
identifier: a
times
left parenthesis
identifier: b
minus
integer constant: 17
right parenthesis
white space, length 1
plus
white space, length 1
integer constant: 5
div
identifier: c