Midterm

Write a Bash or Perl script to translate the file permissions from octal format to symbolic format. Accept the user input interactively. For example, if the user enters "7" then the script outputs "rwx"; if the permission number is invalid, display "invalid".

#! /bin/bash echo "Enter the octal format of file permission: " read b if [$b -gt 7]; then echo "File Permission: invalid" exit fi loop=1 perm="" while [$b -gt 0]; do let x=$b%2 if [$loop -eq 1] && {$x -eq 1]; then perm=$perm"r" else if [$loop -eq 2] && [$x -eq 1]; then perm=$perm"w" else if [$x -eq 1]; then perm=$perm"x" fi fi fi let b=b/2 let loop=loop+1 done echo "File Permission: " $perm

Convert the following permission to its equivalent octal value format: "rwxr-xr--" =

754

Which of the following is NOT a valid operator for redirecting standard input and output?

<=

Linux is a free version of Unix System V.

False

The command alias cannot have the same name as an existing shell built-in command.

False

The inode block stores information including file name, owner, permissions, etc.

False

To change the permissions on a file you type chmode.

False

We can use the "type" command to tell if a file is a soft link.

False

Every directory has these two files: "." and ".."

True

Fedora is a version of Linux.

True

It's possible that we can modify a file but cannot delete it.

True

The X Window System is an independent program and not a part of the Linux kernel.

True

The read and write file permissions do not apply to the "root" user.

True

Which of the following is not a component of the X Window system?

X Screen

Which of the following is the least necessary part for Linux/Unix operations?

X Window

Which of the following is not a desktop environment for Linux?

X.org

Which of the following expression is evaluated to "false", assuming the variable "var1" is assigned a value of "100" (Bash shell)? var1=100

[[ $var1 != 100 && var1 = 100 ]]

Which of the following command cannot be used to retrieve any inode information at all?

cat

Question 18 options: There is a file "IT4983" in my home (personal) directory. I don't know my current working directory. How can I find out the file type of "IT4983" (e.g. a text file, a link, or a directory?) without knowing my current working directory? Use one command only

find / -name "IT4983"

Question 25 options: Referring to Figure 1, what is the result of the command below? ls /orca/seyfarth/.* -ld | wc -l

listing the content of the directory /orca/seyfarth/.* (starting with everything that starts with .), taking all files into consideration. -ld list the dir using long list format, while | wc -l places the content into wc format and counts the lines.

You working directory is "orca". Use one command to create a soft link named "shortcut" in the "css" directory which links to the "students" file in "css343"

ln -s /orca/seyfarth/homework/css343/students/orca/css/ shortcut

Which of the following command produces a significantly different result from other 3 commands?

ls m* -l | grep "^d"

Assuming the current working directory is "homework", use one command to move the "grades" file in "css343" to the "css360" directory and rename it to "grades_360":

mv /css343/grades /css360/grades_360

You current directory is "/". How to delete the "Seyfarth" directory and all contents in it using one command?

rm -rf /orca/seyfarth

The following is part of a terminal display. Explain the error message. Why is there such an error? Which file(s) would a subsequent "ls" command display? #> lsabc abd abe abf Abg absence apple water #> rm ab* absence applerm: cannot remove 'absence': No such file or directory

rm is the command to remove the proceeding files. Given this situation, ab* matches all files starting with ab and removes them. Since ab comes before absence, the error message appear as absence begins with ab and ab has already been removed. Since apple does not begin with apple, it is then removed in order. In the first line, everything would be removed except Abg and water. Linux is case sensitive and would not remove Ab as it does not match the ab call for removal.

Which of the following is NOT a valid Linux file name?

user/home

What's the output result of the script below: #!/bin/bash var1=20 var2=10 var3=var1+var2 let var4=var1-var2 echo var3=$var3 printf '$var4=$var1-$var2' echo ="$var1-$var2=$var4"

var3=var1+var2 $var4=$var1-$var2=20-10=10