Unix/Linux Command Line Basics: Shell, Files, and Navigation

Echo command to find current shell?

echo $SHELL or echo $0

Command to append output to existing file?

>> (Example: ls >> file.txt)

Command that displays your username?

whoami

ls command to list all files including hidden?

ls -a

Pathname starting with slash is called?

Absolute pathname

True/False: Relative pathname begins with slash

FALSE

What does cd with no arguments do?

Changes to home directory

Unix file system structure type?

Hierarchical or tree-like

Default directory when you log in?

Home directory

Directory navigation - what is dot?

Current directory

Directory navigation - what is dot-dot?

Parent directory (up one level)

Command for help about other commands?

man (manual pages)

Hidden files start with what symbol?

Dot (.)

Echo command to display shell name?

echo $0

Valid syntax for man pipe to less?

man ls | less

How to display value of variable TOTAL?

echo $TOTAL

What does echo $PATH display?

Colon-separated list of executable directories

ls option to display permissions?

ls -l

Program not in search path result?

command not found error

Command to change file permissions?

chmod

Commands to change to home directory?

cd, cd ~, cd $HOME

Command to copy a file?

cp

Command for file type/classification?

file

Display text one screen at a time?

less or more

Find files by name in directory tree?

find

Link command syntax?

ln source_file link_name

Output text file contents?

cat

Search patterns in file?

grep

List files/subdirectories recursively?

ls -R

Create new directory?

mkdir

Rename or move file?

mv

Display logged-in users?

who or w

Remove non-empty directory?

rm -r directory_name

Delete a file?

rm

True/False: touch creates file if doesn't exist

TRUE

Script PID variable?

$$

All command-line arguments variable?

$* or $@

Number of arguments variable?

$#

Script name variable?

$0

Create shell variable syntax?

VARNAME="value" (no spaces)

Variable initialization syntax?

VARNAME="value" (no spaces around =)

Echo pipe to more does what?

Paginates output

Single vs double quotes difference?

Double allows variables, single literal

Read input command first method?

read variablename

Read input command?

read

$HOME contains?

Absolute pathname of home directory

find -name option purpose?

Search by filename

List only hidden files?

ls -d .*

Metacharacter for zero or more?

* (asterisk)

Metacharacter for exactly one?

? (question mark)

Pipe metacharacter?

| (vertical bar)

Exit Vim insert mode?

ESC

Enter Vim insert mode?

i, a, or o

Vim startup mode?

Native/Command Mode

Enter Vim command-line mode?

: (colon)

Vim save and quit?

:wq

Vim delete current line?

dd

True/False: Vim only opens existing files

FALSE

Display directory and hidden files?

ls -a

True/False: Symbolic links only to files

FALSE (directories too)

Owner execute in ls -l position?

Position 4

How to read ls -l output?

Positions 2-4 owner, 5-7 group, 8-10 others

Group name in ls -l?

Fourth field

Group permissions positions?

Positions 5-7

Others execute position?

Position 10

chmod 755 result?

rwxr-xr-x

Understanding chmod changes?

755=rwxr-xr-x, 644=rw-r--r--

True/False: User can chmod own files

TRUE

True/False: Only owner can view permissions

FALSE

True/False: Root can modify any permissions

TRUE

rmdir removes what?

Empty directories only

True/False: touch resets permissions

FALSE (updates timestamps)

Non-blank character sequence called?

Token or word

True/False: Bash options start with dash

TRUE

True/False: pwd has zero arguments

TRUE

True/False: echo is built-in

TRUE

Redirect ls -l to file?

ls -l > ls-out

Shebang line for bash?

#!/bin/bash

Run script in current directory?

./scriptname

Run function my_func?

Type: my_func

Alias command syntax?

alias name="command"

grep vs cat output?

grep shows matching lines, cat shows all

Startup configuration file?

.bashrc or .bash_profile

True/False: echo $HOME works (uppercase)?

TRUE (case-sensitive)

True/False: Symbolic links only to files (2nd Q)

FALSE

True/False: Only owner changes permissions

FALSE (root can too)

True/False: Script variables global by default

TRUE

Define function named test?

test() { commands; }

Functions persist between sessions?

FALSE

Export command purpose?

Makes variables available to sub-processes