1. What does the shell ordinarily do while a command is executing? What should you do if you do not want to wait for a c

[answerhappygod]

1. What does the shell ordinarily do while a command is
executing? What
should you do if you do not want to wait for a command to finish
before
running another command?
2. Using sort as a filter, rewrite the following sequence of
commands:
$ sort list > temp
$ lpr temp
$ rm temp
3. What is a PID number? Why are these numbers useful when you run
processes
in the background? Which utility displays the PID numbers of the
commands
you are running?
4. Assume the following files are in the working directory:
$ ls
intro notesb ref2 section1 section3 section4b
notesa ref1 ref3 section2 section4a sentrev
Give commands for each of the following, using wildcards to express
filenames
with as few characters as possible.
a. List all files that begin with section.
b. List the section1, section2, and section3 files only.
c. List the intro file only.
d. List the section1, section3, ref1, and ref3 files.
5. Refer to the info or man pages to determine which command
will
a. Display the number of lines in its standard input that contain
the word a
or A.
b. Display only the names of the files in the working directory
that contain
the pattern $(.
c. List the files in the working directory in reverse
alphabetical order.
d. Send a list of files in the working directory to the printer,
sorted by size.
6. Give a command to
a. Redirect standard output from a sort command to a file
named
phone_list. Assume the input file is named numbers.
b. Translate all occurrences of the characters [ and { to the
character (, and
all occurrences of the characters ] and } to the character ), in
the file
permdemos.c. (Hint: Refer to the tr man page.)
c. Create a file named book that contains the contents of two
other files:
part1 and part2.
7. The lpr and sort utilities accept input either from a file named
on the command
line or from standard input.
a. Name two other utilities that function in a similar manner.
b. Name a utility that accepts its input only from standard
input.
8. Give an example of a command that uses grep
a. With both input and output redirected.
b. With only input redirected.
c. With only output redirected.
d. Within a pipeline.
In which of the preceding cases is grep used as a filter?
9. Explain the following error message. Which filenames would a
subsequent
ls command display?
$ ls
abc abd abe abf abg abh
$ rm abc ab*
rm: cannot remove 'abc': No such file or directory
10. When you use the redirect output symbol (>) on a command
line, the shell
creates the output file immediately, before the command is
executed. Demonstrate
that this is true.
11. In experimenting with variables, Max accidentally deletes
his PATH variable.
He decides he does not need the PATH variable. Discuss some of
the
problems he could soon encounter and explain the reasons for these
problems.
How could he easily return PATH to its original value?
12. Assume permissions on a file allow you to write to the file
but not to delete it.
a. Give a command to empty the file without invoking an editor.
b. Explain how you might have permission to modify a file that
you cannot
delete.
13. If you accidentally create a filename that contains a
nonprinting character,
such as a CONTROL character, how can you remove the file?
14. Why does the noclobber variable not protect you from
overwriting an
existing file with cp or mv?
15. Why do command names and filenames usually not have embedded
SPACEs?
How would you create a filename containing a SPACE? How would
you
remove it? (This is a thought exercise, not recommended practice.
If you
want to experiment, create a file and work in a directory that
contains only
your experimental file.)
16. Create a file named answer and give the following
command:
$ > answers.0102 < answer cat
Explain what the command does and why. What is a more
conventional
way of expressing this command?