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Preliminary exams open source tech
Science Technology and Society (STS)
ICCT Colleges Foundation
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PRELIMINARY EXAMINATION REFERENCE
(OPEN SOURCE TECHNOLOGIES)
Prepared by: NELFREDO V. SEVILLA
SHELL is a program that takes keyboard commands and passes them to the operating system to carry out
BASH is an acronym for Bourne Again SHell. It is an enhanced replacement for sh, the original Unix shell program written by STEVE BOURNE
TERMINAL EMULATOR is another program needed to interact with the shell when using Graphical User Interface
SHELL PROMPT is appeared whenever the shell is ready to accept input
PARTS OF THE SHELL PROMPT username@machinename ~$
COMMAND HISTORY is a previous command that reappears once you press up arrow
500 COMMANDS are commands that most Linux distributions can handle on its history
date is a command used to display current date and time
cal is a command used to display a calendar of the current month
df is a command used to see the current amount of free space on your disk drives
free is a command used to display the amount of the free memory
exit is a command used to end a terminal session
HIERARCHICAL DIRECTORY STRUCTURE
is a tree-like pattern of directories which may contains files and other directories
ROOT DIRECTORY is the first directory in the file system
pwd is a command used to display the current working directory
ls is a command used to list the files and directories in the current working directory
cd is a command used to change a current working directory
PATHNAME is the route that take along the branches of the tree to get to the directory wanted
TWO TYPES OF PATHNAMES relative or absolute
RELATIVE PATHNAME is a pathname that starts from working directory and leads to its destination
. or (DOT) is a special symbol that represents working directory
.. or (DOT DOT) is a special symbol that represents working directory’s parent directory
ABSOUTE PATHNAME
is a pathname that starts from the root directory and follows the tree branch by branch until the path to the desired directory or file is completed
cd is a command used to change the working directory to your home directory
cd - is a command used to change the working directory to the previous working directory
~ is a symbol that represents home directory
OPTIONS is a keyword used to change a command’s behaviour
COMMON LS OPTIONS
-a is an option used to list all files even those names that begins with a period (hidden)
-A is an option like -a but it does not include. (DOT) and .. (DOT DOT)
-d is an option used to see the details about the directory rather than its contents
-F is an option used to append an indicator character to the end of each listed name
-h is an option used to display file sizes in human readable format rather than in bytes
-l is an option used to display result in long format
-r is an option used to display the result in reverse order
-s is an option used to display the result sorted by file size
-t is an option used to display the result sorted by modification time
file is a command used to determine a file’s type
less is a command used to view text files
DIRECTORIES FOUND ON LINUX SYSTEMS
/ root directory where everything begins
/bin contains binaries (programs) that must be present for the system to boot and run
/boot contains the Linux kernel, initial RAM disk image and the bootloader
/dev contains device nodes
/etc contains all of the system-wide configuration files
/home is a directory that is given to each user
/lib contains shared library files
/media contains mount points for removable media (used by modern Linux systems)
/mnt contains mount points for removable media (used by older Linux systems)
/opt contains optional software to hold commercial software products
/sbin contains system binaries that perform vital system tasks
/usr contains all the programs and support files used by regular users
/tmp contains temporary and transient files created by various programs
/usr/bin contains executable programs
cp is a command used to copy files or directories
mv is a command used to move or rename files or directories
whatis is a command used to display a very brief description of a command
info is a command used to display a program’s info entry
alias is a command used to create your own command
I/O REDIRECTION allows us to change where output goes and where input comes from
TWO TYPES OF I/O REDIRECTION OPERATORS
> is a redirection operator that means to overwrite
>> is a redirection operator that means to append or modify
cat is a command used to concatenate files; also used to view text in standard output
ctrl-D is a keyboard combination that tells cat command that it has reached the EOF
PIPELINES is a shell feature that utilizes the ability of commands to read data from standard input and send to standard output
| is a pipeline operator used to pipe the standard output of a command into the standard input of another
FILTERS take input, change it somehow and then output it
sort is a filter command that is used to view the output in sorted order
uniq is a filter command that is used to omit or report repeated lines
wc is a filter command that is used to display the number of lines, number of words and bytes contained in a file grep (Globally search a Regular Expression and Print) is a powerful program or command used to find text patterns within files
head is a command used to print the first ten lines (default) of the output
tail is a command used to print the last ten lines (default) of the output
EXPANSION
is something that is expanded into something else before the shell acts upon it
echo it a command that performs a very simple task and it prints out its text arguments on standard output
PATHNAME EXPANSION is the mechanism by which wildcard works
TILDE EXPANSION
is when used at the beginning of a word then it expands into the name of the home directory of the named user
ARITHMETIC EXPANSION allows us to use the shell as calculator. $(( expression ))
ARITHMETIC OPERATORS IN SHELL +,-, *, /, %, **
BRACE EXPANSION
allows you to create multiple text strings from a pattern containing braces. PREAMBLE { RANGE } POSTSCRIPT
PREAMBLE is a leading portion on the patterns to be expanded
POSTCRIPT is a trailing portion on the patterns to be expanded
PARAMETER EXPANSION allows you to reveal the contents the variables. $ VARIABLENAME
COMMAND SUBSTITUTION allows you to use the output of a command as an expansion. $( command )
QUOTING
is used to control the use of expansion and to suppress unwanted expansions
WORD-SPLITTING removes extra whitespaces from echo command’s list of arguments
DOUBLE QUOTES is the type of quoting that if you place text inside, all special characters lose their meaning and are treated as ordinary characters EXPANSIONS BEING SUPPRESSED BY DOUBLE QUOTES word-splitting, pathname, tilde, brace
EXPANSIONS STILL CARRY OUT BY DOUBLE QUOTES parameter, arithmetic, command substitution
SINGLE QUOTE is the type of quoting that suppress all expansions
ESCAPE CHARACTER is the quoting that is used if you want to quote a single character
OPEN SOURCE TECHNOLOGY
is defined as the production and development philosophy of allowing end users and developers to not only to see the source code of software, but to modify it as well
THREE CHARACTERISTICS OF OPEN SOURCE SOFTWARE free to use, free to modify, free to redistribute
CLOSED SOURCE SOFTWARE
means computer programs whose source code is not published and not shared for everyone to look and change; a proprietary software
Preliminary exams open source tech
Course: Science Technology and Society (STS)
University: ICCT Colleges Foundation
