Grade histograms
Write the following shell scripts. When you're done, bundle them all
up with shar and mail them to the Guest TA. In your shell
scripts, you may only use the following:
- Any internal shell command (e.g. echo, for, etc).
- cat, head, tail, sort, bc,
sleep, kill, expr.
You may not write any C programs to help yourself out,
nor are you allowed to use any other Unix programs (like sed
or perl) in your scripts.
Finally, your program should handle errors gracefully. For example,
if the command line arguments are supposed to be files, and the user
specifies a non-file, you should print a descriptive error message on
standard error, and either exit or not exit as you see fit.
- revarg: This script prints out its command line arguments
in reverse order all on one line.
- sortfl: This script treats the command line arguments as
filenames. It sorts the filenames, and then for each file, it prints
the file's name, the first line of the file, the last line of the file,
and a blank line.
- lsfiles: This script takes a list of files as its command
line arguments. For each file, it first prints out the file's name,
then it prints out any word in the file that is the name of an existing
file (or directory) in the system. Then it prints out a blank line.
- lsnums: This script prints out a sorted list of all words
in standard input that can be treated as non-zero numbers. Make the
list sorted numberically, not lexicographically.
- square: This script takes a number as its command line
argument. Call this number n. The script prints out lines
of the form ``i i*i'' for each i from zero to n.
- timex: This script takes a shell command on its command
line argument, and executes it in the background. It then waits one
minute, and if after one minute, the command has not exited, it kills
it with kill -9. You'll have to use kill to determine
if the process is still alive (read the man page). You cannot
use ps or write your own C program to test for the existence of
a process.
Additionally, you should be able to call timex in the following
manner:
timex -t sec command
This has timex sleep for sec seconds instead of 60.
Don't worry about preserving multiword arguments (i.e. arguments
with spaces in them) when you execute the command. In other
words, if I say
timex echo 'Jim Plank'
it's ok if the output is
Jim Plank
Working Examples
Working examples are in the directory
/home/cs494/labs/Sh/programs.
You can run these only on kenner.
I've doctored it so that you can't read the programs. (Can any CS360 people
figure out how I did this?).
