starts with a slash (/), which represents the root directory. The slash is followed by the name of a file located in the root directory. An absolute pathname can continue, tracing a path through all intermediate directories, to the file identified by the pathname. String all the filenames in the path together, following each directory with a slash (/). This string of filenames is called an absolute pathname because it locates a file absolutely by tracing a path from the root directory to the file.
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Relative Pathname
traces a path from the working directory to a file. The pathname is relative to the working directory. Any pathname that does not begin with the root directory (represented by /) or a tilde (\~) is a relative pathname
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3 ways to return to your home directory
cd \~, cd, cd $HOME
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What‘s the arrangement of directories and files in the unix system?
a tree-like structure called the file system, called a directory tree. At the very top of the file system is a directory called “root” which is represented by a “/”. All other files are “descendants” of root.
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What directory does it take you to when you first log in?
The home directory.
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What’s the command that gives helpful information on a utility?
man (eg: ‘man cat’ will display a manual on the cat utility)
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What symbol do hidden files in a directory start with?
dot character (.)
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What’s the command that tells you the current name of the shell?
echo $0 (returns -bash)
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Set a variable value in a borne shell. How do you display the variable?
echo $variname
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What does echo $PATH display?
Which directories your shell is set to check for executable files. $PATH is the list of said directories.
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What is the command and option that lets you see all the meta information of a file?
ls -l filename
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Inside a borne shell script, what’s the symbol used for the PID?
$$
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What’s the command that can be used to change permission information for a file?
chmod
syntax: chmod a+r filename (makes filename readable to all)
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What’s the command that copies files?
cp
syntax: cp ogfile copyfile
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What’s the command that is used to tell the type information of a file?
file
eg: file filename (displays filename: ASCII text)
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What’s the command used on a file to display one page of information of the file contents at a time?
more or less (less allows you to scroll up, more does not)
eg: cat filename | less
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What’s the command to make soft links?
ln -s filename linkname
Allows multiple filenames to be linked to a file
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What’s the command that outputs the contents of a text file?
cat filename
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What’s the command that searches for patterns in a text file?
grep string filename
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Basic redirection syntax.
cat > filename
Create a file called filename. Type the desired input and press CTRL+D to finish. The text will be in file filename.
cat < filename
Just cats the content of filename.
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What is the command that makes a new subdirectory/directory?
Mkdir dirName
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What’s the command that removes a file? Moves a file?
rm filename
mv filename newfile
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What’s the command that displays the information about the users logged into the system?
who
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What’s the command that deletes a non-empty directory?
rmdir or rm -d
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If I touch a file name, and the file name doesn't already exist, does touch create it?
Yes, touch creates an empty file.
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If you set the variable value in the shell and you want a program/script to read and display it, what command do you have to do on the variable to make it available to the script?
export
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How do you read in a value in a shell prompt?
read
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What does the command “find” do? find -name?
used to find files and directories and perform subsequent operations on them. It supports searching by file, folder, name, creation date, modification date, owner and permissions.
\ find -name searches filenames specifically.
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What is the command to list all the files in your working directory that start with a dot?
ls -a lists all files including hidden files that start with a dot. do not try ls .\* it broke my thing
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Metacharacter for pipe?
|
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Which key stroke will enter command mode in VIM?
esc
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in VIM, which keystroke will allow you to enter editor mode?
i
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What mode is VIM in at first?
command mode
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Command to write (save) the contents of the files then quit the editor?
esc :wq!
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What symbols do commands start with in VIM?
\:
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Can you chmod a file you don’t own?
No
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Can you list metadata on files you don’t own?
Yes
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What is a root?
A user that can do anything (ex: chmod any file)
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What does touching an already existing file do? Does it reset it’s permissions?
if the file existed beforehand, touch will not change its permissions, just update its last edited timestamps
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What is a token?
A non blank character/sequences of characters
\ A token is made up of ordinary characters, or of operator characters ()<>&|;, but not both. For example, foo
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What symbol do options start with?
\-
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Identify commands with 0 arguments.
cd, pwd
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What is an example of a built-in command?
echo, cd
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How do you do piping?
A pipe is a form of redirection (transfer of standard output to some other destination). Allows you to use 2 commands at once
ex: history | tail
calls history command and tail to display the last 10 executed commands
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What’s the comments you need on the first line of the script to ensure it gets executed on the bash shell?
\#!/bin/bash
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What are the 2 metasymbols you have to put at the beginning of a script for it to run correctly?
./
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What’s the syntax for creating an alias?
alias ‘someAlias=someCommand’
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What does grep do? Syntax?
Identifies line with requested string.
grep “l” filename
works on directories to search file names
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Which file do you save variables, functions, and aliases to so they are available upon log in?
In the \~/.bashrc file
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What are the single dot and double dot directory entries?
mkdir automatically adds these 2 entries.
The . is synonymous with the pathname of the-working directory and can be used in its place; the .. is synonymous with the pathname of the parent of the working directory. These entries are hidden because their filenames begin with a period.
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num=875
number1=”Add $num”
number2=’Add $num’
\ What will echo $number1 and echo $number2 display?
Add 875
Add $num
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ls -l info idk just memorize this
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chmod symbols (just memorize this too)
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Do I have to put symbols in front of a function name to run it or can I just put the name of the function?
Just name of function.
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What is the shell metacharacter that matches 0 or more characters?
\*
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What is the shell metacharacter that matches 1 character?
?
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Inside a script, what are the symbols that contain the arguments on the command line to the script?
$1, $2, … , $n for each argument n on the command line
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