6.6. Exercises
See Section A.5, "Answers to Chapter 6 Exercises" for answers to the following
exercises:
-
[7] Write a program that acts like cat, but
reverses the order of the output lines. (Some systems have a utility
like this named tac.) If you run yours as
./tac fred barney betty, the output should be all
of file betty from last line to first, then
barney and then fred, also from
last line to first. (Be sure to use the ./ in your
program's invocation if you call it tac, so
that you don't get the system's utility instead!)
-
[8] Write a program that asks the user to enter a list of strings on
separate lines, printing each string in a right-justified
20-character column. To be certain that the output is in the proper
columns, print a "ruler line" of digits as well. (This is
simply a debugging aid.) Make sure that you're not using a
19-character column by mistake! For example, entering
hello, good-bye should give
output something like this:
123456789012345678901234567890123456789012345678901234567890
hello
good-bye
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[8] Modify the previous program to let the user choose the column
width, so that entering 30,
hello, good-bye (on separate
lines) would put the strings at the 30th column. (Hint: see the
section Section 2.6.1, "Interpolation of Scalar Variables into Strings" in Chapter 2, "Scalar Data" about controlling variable interpolation.) For
extra credit, make the ruler line longer when the selected width is
larger.
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