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TestOut Linux Pro Exam
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TestOut Linux Pro Exam
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TestOut Linux Pro Exam |Linux shell - ANSWER a program that traditionally provides the text user interface
(TUI) for Linux. The term shell is descriptive, since it is considered an outer layer of
the operating system. The shell is the interface between you, a user or administrator,
and the internal parts of the operating system including its very core which is the
kernel. The shell's main function is to read and parse your commands and then to
execute them through interactions with the Linux kernel.
From the Console (The keyboard and monitor attached to a computer running Linux)
- ANSWER Press the following key combinations:
Ctrl+Alt+F1 (in some Linux distributions, Alt+F1) will start or switch to the first Linux
shell session.
Ctrl+Alt+F2 through Ctrl+Alt+F6 (in some Linux distributions, Alt+F2 through Alt+F6)
will switch to the second through sixth shell sessions.
While Linux distributions will vary, in most cases when a GUI is installed, it will use
the first console session. Use Ctrl+Alt+F1 to switch to a graphical login screen. If you
are already logged in, Ctrl+Alt+F7 will switch to the desktop GUI.
From a desktop GUI - ANSWER Open a terminal session from the applications
menu.
sh - ANSWER The Bourne shell is the oldest Linux shell, but is not widely used.
This shell was developed for UNIX in the 1970s.
bash - ANSWER The Bourne-again shell (Bash) is the default shell used by most
Linux distributions. It uses commands similar to a UNIX shell. The Bash includes:
Command and file name completion when pressing the Tab key
Command history
zsh - ANSWER The Z Shell (zsh) is an improved version of Bash and is available
on many Linux distributions.
shh - ANSWER The Bourne shell (sh) is an earlier version of bash, and is similar in
many ways. The sh shell was originally created by Steve Bourne.
ksh - ANSWER The Korn shell (ksh) provides scripting features not found in Bash.
Ksh was developed by David Korn.
csh - ANSWER The C-shell (csh) uses syntax similar to the syntax used in the C
programming language.
tcsh - ANSWER The tcsh shell is an improved version of csh. It offers command
line editing and completion features that are not available in csh.
/etc/shells - ANSWER If a shell type is installed, it will be listed in the /etc/shells file.
You can switch to any shell by typing the shell's name. For example, type ksh within
any shell to switch to the Korn shell.
, echo $SHELL - ANSWER The echo $SHELL command returns the default or
preferred shell. The environment $SHELL holds the user's preferred shell which is
typically set in /etc/passwd. For example, if bash is the user's preferred shell,
$SHELL will hold the value, /bin/bash. The preferred shell does not change when
you switch shell types.
echo $0 - ANSWER The echo $0 command can be used to return the current shell
type. The special variable $0 normally holds the command used to start a script. A
shell session is initiated by a script. Consequently, $0 will hold the name of the script
which is consistent with the shell type. For example, $0 in a console session running
bash might hold the value -bash, $0 in a terminal application opened from a desktop
menu might hold the value bash. When you type ksh, the ksh script is run, a Korn
shell session is opened and $0 will hold the value ksh.
all shells share some common characteristics: - ANSWER The shell provides a
command line interface that allows the user to interact with the Linux kernel.
A Linux system can run multiple shell sessions at the same time.
One shell session can run within another shell session. This may be done
interactively, such as when a user starts a second shell from the first shell's
command line, or automatically, by scripts or programs.
Shells use configuration files to establish their operating environments.
bash shell default command line prompt - ANSWER The username of the current
user
The @ symbol
The hostname
A space
The base name of the current working directory
~ - ANSWER If the current working directory is the home directory (the default
directory when the user first logs in), the tilde symbol (~) is displayed instead.
# character - ANSWER indicates that the current user is the root user.
$ character - ANSWER indicates that the current user is a normal user.
$PATH environment variable - ANSWER contains the set of directories that are
searched when you type an executable file at the shell prompt.
The shell does not look in the current working directory for the executable file.
To see the list of directories, type echo $PATH at the shell prompt.
To add a directory to a path, type PATH=$PATH:[directory_path] and then type
export PATH.
Type the filename at the shell prompt. (run an executable) - ANSWER Resides in a
directory that is included in the $PATH environment variable
Type ./ followed by the filename. (run an executable) - ANSWER Resides in the
current working directory and the current directory is not included within the path
environment variable
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