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.ft B
.tl 'CSCI-E28'Assignment 0'Not to be turned in'
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.hy 14
.na
\fBIntroduction\fR
.sp 6p
The purpose of this assignment is to review basic Unix and C skills
and help you figure out if you are prepared for this course.  Work
through the following exercises.  You should of course feel free to
refer to any Unix/C books and/or on-line documentation you like.
You should find the C exercises pretty easy.  If you don't, think
carefully before enrolling.  You should find the Unix exercises
easy or you should be able to locate the information in the manuals.
If you don't, find a good Unix book and start exploring.
.sp 6p
Solutions to these problems will be available at the second lecture.
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\fBThe Exercises\fR
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.ti -\w'1. 'u
1. Explain the purpose of the following Unix commands: \fCls, cat, rm,
cp, mv, mkdir, cc\fR.

.ti -\w'2. 'u
2. Using your favorite editor, create a small text file.  Use \fCcat\fR to
create another file consisting of five repetitions of this small text file.
.sp 6p
Use \fCwc\fR to count the number of characters and words in the original
file and in the one you made from it.  Explain the result.
.sp 6p
Create a subdirectory and move the two files into it.
.sp 6p
.ti -\w'3. 'u
3. Create a file containing a directory listing of both your home directory
and the directory \fC /bin\fR.
.sp 6p
.ti -\w'4. 'u
4. Devise a single command line that displays the number of users currently
logged onto your system.
.sp 6p
.ti -\w'4. 'u
5. Write, compile, and execute a C program that prints a welcoming message
of your choice.
.sp 6p
.ti -\w'6. 'u
6. Write, compile, and execute a C program that prints its arguments.
.sp 6p
.ti -\w'7. 'u
7. Using \fCgetchar()\fR write a program that counts
the number of words, lines, and characters in its input.
.sp 6p
.ti -\w'8. 'u
8. Create a file containing a C function that prints the message 
\fC"hello, world"\fR.  Create a separate file containing the main
program which calls this function.  Compile and link the resulting
program, calling it \fChw\fR.
.sp 6p
.ti -\w'9. 'u
9. Look up the entries for the following topics in your system's manual;
the \fCcat\fR command, the \fCprintf\fR function, and the \fCwrite\fR
system call.
.sp 6p
.ti -\w'10. 'u
10. \fIYou Must Try This One\fR\ \ 
There are two parts to the problem.  If you are not able to do the
first part of this problem, you are not prepared to take this class.
If you find the second part extremely tricky, you will find the
assignments for the course difficult and potentially more time consuming
than you expect.
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.ti -\w'part 1 'u
part 1 Write a program that prints a range of lines from a text file.
The program should take command line arguments of the form:
.sp 3p
.ft C
.ps 8p
        lrange 10 20 filename 
    \fRor\fC lrange 10 20
.ps 10p
.ft R
.sp 3p
will print lines 10 through 20 of the named file.
If there is no named file, the program should print lines read from standard
input.
If there are not enough lines in the file, the program should
print what it can.
.sp 6p
Your program should work for input with any number of lines.
.br
Your program should work for lines of any length.
.sp 6p
.ti -\w'part 2 'u
part 2 Write a program called \fClast10\fR that prints the last
ten lines of a text file.  The program can be used from the
command line with:
.sp 3p
.ft C
.ps 8p
    last10 filename
.ps 10p
.ft R
or
.ft C
.ps 8p
    last10 
.ps 10p
.ft R
.sp 3p
If there is no filename, last10 processes standard input.
.br
Your program should work for input with any number of lines.
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.tl '''continued \(->'
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.tl 'CSCI-E28'Skill Assessment Exercises'page %'
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.ti -\w'11. 'u
11. \fIStructs and Pointers\fR\ \ You must try this one, too.
Write a function that computes some basic statistics for a list of
numbers and stores those results in parts of a struct.  In particular,
given this definition:
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.nf
.ft C
.ps 8p
.vs 10p
struct numlist {  float *list;   /* points to list of numbers */
                  int   len;     /* number of items in list   */
                  float min,     /* the minimal value in list */
                        max,     /* the maximal value in list */
                        avg;     /* the mean of the numbers   */
		};
.vs 12p
.ps 10p
.ft R
.fi
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.sp 4p
write a function \fCcompute_stats(struct numlist *listptr)\fR that
takes as an argument a pointer to a struct numlist with \fIlist\fR and \fIlen\fR
already initialized and computes and fills in the other three members.
Write a program that uses your function to process user input and display 
results.

.ti -\w'12. 'u
12. \fIDynamic memory management\fP:  Write a C program that reads in an arbitrary number
of lines then prints those lines in reverse order.  The lengths of the lines may be
limited to a fixed maximum. but the number of lines is limited only by system memory
available.  
.sp 6p
For a slightly greater challenge, support
a \fB-b\fP command line option that causes each line to be printed out
backwards.
.sp 6p
The program, like most Unix tools, reads from a file if a filename is given
or from standard input if no filename is given on the command line.
.sp 8p
Running this program on its own output should produce the original input.
For example
.sp 4p
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.nf
.ft C
.ps 8p
.vs 10p
 ./reverse /etc/passwd | ./reverse > rev2
 diff rev2 /etc/passwd
.vs 12p
.ps 10p
.ft R
.fi
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.sp 4p
should show no differences.
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