Topic 5 - The command-line interface Flashcards
1
Q
what is the outcome of typing
Grep ‘sat’ -I ‘datefile’
into a linux terminal
A
in a linux terminal:
this will search for the text pattern ‘sat’ while ignoring letter cases in the file named ‘datefile’
2
Q
this is used to redirect the STDOUT (standard out stream) of a command to a file
A
what is the > symbol used for
3
Q
Standing for ‘global regular expression print’. is a tool for finding a given text pattern in a given text.
Text can be pipelined into this command or can be held inside a file
A
describe the linux
grep
command
4
Q
give a description of the linux
cat
command
A
this command will concatenate files and print on the standard output
5
Q
what is the outcome of typing
Touch existing-filename
into a linux terminal
A
in a linux terminal:
this will update the access and modification timestamps of the given filename
6
Q
what is the name and purpose of the ~ symbol in linux
A
in linux this is called a
tilde and points / references your home directory
7
Q
in a linux terminal:
this will redirect the output from the date command into the given filename, creating a new file if it does not exist
A
what is the outcome of typing
Date > filename
into a linux terminal
8
Q
in a linux terminal:
this will update the access and modification timestamps of the given filename
A
what is the outcome of typing
Touch existing-filename
into a linux terminal
9
Q
The OS is also able to optimize this efficiently since the output of one command can be written to main memory and as soon as data starts to arrive the other command can start to consume it without the need for the first command to finish execution
A
how can the operating system
optimize pipelining
10
Q
the shell used on this was named sh (bourne shell) as was written by stephen bourne
A
what was the shell used on UNIX systems called and who created it
11
Q
what is the outcome of typing
Rm filename -f
into a linux terminal
A
in a linux terminal:
this will suppresses the prompt confirming removal of write protected files and overrides the write protection. in turn deleting the file
12
Q
what is the outcome of typing
Cp my-file my_directory
into a linux terminal
A
in a linux terminal:
this will copy the file my-file into the directory my-directory
13
Q
this is a file that contains the paths of available shells on the linux system
A
describe the linux
/etc/shells
file
14
Q
when this occurs the operating system will set:
- the input stream as the keyboard
- the output stream as the terminal window
A
when a terminal is opened what are the default input and output streams configured by the operating system
15
Q
give a description of the linux
mv
command and how it works
A
in a linux terminal:
This is used to move files and directories. If the source file given is moved to the same location this command then renames the file using the destination
16
Q
• it prompts a user to type a command line
• it deals with editing within the line, accepting the line when Enter is pressed
• some special characters are picked out and handled specially, such as:
◦ quotation marks preserve spaces but are themselves stripped out
◦ > and ◦ wildcards such as * cause filenames to be expanded
• the completed command line is broken into pieces (tokens) by spaces
• the first token on the line is taken as the command
• if the command is built-in, then:
◦ the corresponding action is taken
• otherwise the file system is searched for a matching filename
• if a matching file is found, then:
◦ the type of file is determined
◦ if the file is a script, then:
– the script commands are interpreted recursively line by line
– until the end of the file
◦ if the file is an executable program:
– a system call obtains a chunk of memory from the memory management module
– a system call loads the contents of the program from the file system into that memory
– the remainder of the command-line arguments are copied to it
– a final system call is made to execute the program, relinquishing control of the processor through a context switch
– until the program ends and a context switch returns control to the shell
• else if no matching file is found, report an error
This process is then repeated.
A
how the linux cli operates
(come back to this at the end of the module)
17
Q
this will redirect the STDOUT (standard output) of the command to a given file.
- If the file contains content it will be overwritten
- if the file does not exist it will be created
A
in a windows and linux terminal what is the (>) used for and 2 considerations to take into account before its use
18
Q
in a linux terminal:
this will make a new directory with the name as the value given
A
what is the outcme of typing
Mkdir value
into a linux terminal
19
Q
this can be used to give STDIN (standard input) to a command from a file for example
A
in a windows or linux terminal what does the (
20
Q
in a linux terminal:
this will tell you the file type of the filename you have given
A
what is the outcome of typing
File filename
into a linux terminal
21
Q
what is the outcome of typing
Ls -l
into a linux terminal
A
in a linux terminal:
this will output detailed information about the contents of the directory
note
- if the first character of a line is a (-) it represents a file
- if the first character of a line is a (d) it represents a directory
22
Q
Because linux was developed from UNIX many of the linux shells maintain traditions from UNIX such as syntax this in turn has kept compatibility alive between linux systems
also many of the linux shells are derivitives of the unix sh shell although they will contain many new features
A
why are commands from UNIX seen in linux
23
Q
what is the outcome of typing
Touch non-existing filename -c
into a linux terminal
A
in a linux terminal:
this will find no file and will also not create a new file. execution ends silently
24
Q
this linux shell
- is a widely used shell in linux distributions
- maintains compatibility with the original sh shell
- maintains compatibility with the original sh shell
A
give three points about the linux:
Bash (bourne again shell)
25
what is the linux
**find**
command used for
in linux terminal:
This is used to search for files in a directory
26
this is a file that contains information about the systems processor
describe the linux
**/proc/cpuinfo**
file
27
this is an accronym for:
**bourne again shell**
what does
**bash**
stand for
28
give 3 reasons as to why many OSs share the same commands which may also have the same or similar functionality
the reason this occurs are
* Developers have been influenced by UNIX and so the UNIX commands and syntax still exist
* Open source software means that a software can be built and then intergrated easily to another OS. Since many cli commands are external programes this is how this is achieved
* compliance with POSIX
29
give an overview description of what
**recursion**
is
This is where a function or process calls itself. It is used with many shell commands for actions such as searching through directories
_example_
function look\_for\_key(box) {
for (item in box) {
if (item.is\_a\_box()) {
look\_for\_key(item);
} else if (item.is\_a\_key()) {
console.log("found the key!")
}
}}
30
what is the **\>** symbol used for
this is used to redirect the STDOUT (standard out stream) of a command to a file
31
describe what
**POSIX (Portable Operating System Interface)**
is
this is a set of standards and utilities maintained by IEEE that aims to maintain compatibility between operating systems. in turn meaning that an application can be run on either OS
The standards can define common APIs as well as how certain operating system tasks tasks should be handled.
Many OSs have some compliance with this
32
this will redirect the STDOUT (standard output) of a command to a given file.
* If the file contains content it will be preserved and the output will be appended to the end of the files content
* if the file does not exist it will be created
in a linux or windows terminal what does the (\>\>) achieve and what are 2 considerations before its use
33
in a linux or windows terminal what does the (\>\>) achieve and what are 2 considerations before its use
this will redirect the STDOUT (standard output) of a command to a given file.
* If the file contains content it will be preserved and the output will be appended to the end of the files content
* if the file does not exist it will be created
34
in a linux terminal:
this will search for the text pattern ‘sat’ while ignoring letter cases in the file named ‘datefile’
what is the outcome of typing
**Grep** *‘sat’* **-I** *‘datefile’*
into a linux terminal
35
in linux this command is used when we would like to switch user accounts this includes logging in to the root account. this command is known as (switch user)
describe the linux
**su**
command
36
why are commands from UNIX seen in linux
Because linux was developed from UNIX many of the linux shells maintain traditions from UNIX such as syntax this in turn has kept compatibility alive between linux systems
also many of the linux shells are derivitives of the unix sh shell although they will contain many new features
37
in a linux terminal:
this will output detailed information about the contents of the directory
_note_
* if the first character of a line is a (-) it represents a file
* if the first character of a line is a (d) it represents a directory
what is the outcome of typing
**Ls -l**
into a linux terminal
38
what is the
**root account**
on linux
this is effectively the administrator account. this account has full control over the system and can carry out any commands
39
give an answer to each of these points concerning
**nano**
* what is it
* under what license is it released
* what would be one appropriate situation for using this
* **what is it** - This is a simple text editor that can be executed and ran inside the terminal
* **under what license is it released** - It is released under the GNU general public license meaning that end users can run, study, share and modify the software
* **what would be one appropriate situation for using this** - Linux has many configuration files written in plain text and using an editor such as this is the recommended approach to take when editing such files
40
in linux this is called a
## Footnote
**tilde and points / references your home directory**
what is the name and purpose of the ~ symbol in linux
41
the syntax is
**Grep** *‘string’* **options** *‘file or files’*
what is the syntax for
## Footnote
**grep**
42
in a linux terminal:
This is used to move files and directories. If the source file given is moved to the same location this command then renames the file using the *destination*
give a description of the linux
**mv**
command and how it works
43
in a linux terminal:
this will find no file and will also not create a new file. execution ends silently
what is the outcome of typing
**Touch** *non-existing filename* **-c**
into a linux terminal
44
what does
POSIX
stand for
this is an accronym for
## Footnote
**Portable Operating System Interface**
45
in linux terminal:
This is used to search for files in a directory
what is the linux
**find**
command used for
46
when this occurs:
1. **the command** - is not aware of anything being different or used
2. **the shell/terminal** - will interpret that this has been used and send the appropriate commands to the OS
3. **the OS** - will receive notification/commands from the shell and switch the STDOUT/STDIN appropriately
when using redirection or piping what are each of these aware of
1. the command
2. the shell/terminal
3. the OS
47
2 options in linux that provide this are
**-i** - known as interactive will prompt the user before each action
**-v** - known as verbose will print to screen confirmation messages
linux commands are executed silently. meaning that unless there is an error or STDOUT then no feedback is given.
## Footnote
**what are 2 options that can provide feedback/security**
48
give 2 points about the linux
## Footnote
**Dash (debian almquist shell)**
this linux shell:
* is an extremely lightweight shell
* maintains compatibility strictly with the sh shell (can be used in place of the sh shell. this maintains compatibility with older scripts that may call sh)
49
give a description of the linux
**touch**
command
50
what is the outcme of typing
**pwd**
into a linux terminal
in a linux terminal:
this prints the current working directory
51
does the sh shell exist on linux
this can be called by scripts on linux but is not strictly available on linux.
instead it is available to call but is symbolically linked to the dash shell
52
this command is used by default to remove files. it however can also be used to remove directories in such a case the -r (recursive) option must be used
give a description of the
**rm**
command and how it handles directories
53
the reason this occurs are
* Developers have been influenced by UNIX and so the UNIX commands and syntax still exist
* Open source software means that a software can be built and then intergrated easily to another OS. Since many cli commands are external programes this is how this is achieved
* compliance with POSIX
give 3 reasons as to why many OSs share the same commands which may also have the same or similar functionality
54
describe the linux
**grep**
command
Standing for ‘global regular expression print’. is a tool for finding a given text pattern in a given text.
Text can be pipelined into this command or can be held inside a file
55
give a description of the
**rm**
command and how it handles directories
this command is used by default to remove files. it however can also be used to remove directories in such a case the -r (recursive) option must be used
56
within this utility:
1. up/down arrow keys - can be used to navigate the text
2. spacebar - is used to view the next page
3. h - is used to get help about the utility
4. q - is used to quit the utility
regarding the linux
**less utility**
what do each of these actions achieve
1. up/down arrow keys
2. spacebar
3. h
4. q
57
what is the outcome of typing
**mv** *my-file my-file2*
into a linux terminal
in a linux terminal:
this will rename the file *my-file* to *my-file2*
58
this is made possible because most commands will use text as thier input and output.
this means that commands can be used flexibly with each other since they are all using text format
what makes pipelining between commands possible
59
regarding the linux
**less utility**
what do each of these actions achieve
1. up/down arrow keys
2. spacebar
3. h
4. q
within this utility:
1. up/down arrow keys - can be used to navigate the text
2. spacebar - is used to view the next page
3. h - is used to get help about the utility
4. q - is used to quit the utility
60
what is the outcome of typing
**Cat** *file1 file2 file3*
into a linux terminal
in a linux terminal:
this will print each of the given files to the terminal in the given order
61
This is where a function or process calls itself. It is used with many shell commands for actions such as searching through directories
_example_
function look\_for\_key(box) {
for (item in box) {
if (item.is\_a\_box()) {
look\_for\_key(item);
} else if (item.is\_a\_key()) {
console.log("found the key!")
}
}}
give an overview description of what
**recursion**
is
62
in a linux terminal:
this will navigate you to the directory/path entered
what is the outcome of typing
**Cd** *path*
into a linux terminal
63
what is the outcome of typing
**Nano** *filename*
into a linux terminal
in a linux terminal:
this will open the file in the nano text editor ready for reading and editing
64
this is effectively the administrator account. this account has full control over the system and can carry out any commands
what is the
**root account**
on linux
65
this directory contains linux configuration files
describe the linux
**/etc**
directory
66
what is the outcome of typing
**Sudo su** *root*
into a linux terminal
this will switch the shell to the root account and give the user full control of the system.
*root* can be omitted since linux will assume *root*
67
This can be dissected into several parts
1. The username
2. The hostname
3. The current directory
4. Privilege. $ for normal privileges, # for superuser privileges
_example_
pi@raspberry:~ $
1. The user is called pi
2. The computer name / hostname is raspberry
3. They are in the home directory
4. They have normal privileges
what are the 4
## Footnote
**parts of a linux prompt**
68
what are the 4
## Footnote
**parts of a linux prompt**
This can be dissected into several parts
1. The username
2. The hostname
3. The current directory
4. Privilege. $ for normal privileges, # for superuser privileges
_example_
pi@raspberry:~ $
1. The user is called pi
2. The computer name / hostname is raspberry
3. They are in the home directory
4. They have normal privileges
69
how do you switch between shells on a linux system
achieving this is simply a case of entering the shell name into the termial
70
give 2 points about the linux:
## Footnote
**Zsh (z shell)**
this linux shell:
* is compatible with bash but offers more customisation
* macOS has recently replaced bash with this shell
71
this is an abbreviation of
‘global regular expression print’
what does
**grep**
stand for
72
what does
**bash**
stand for
this is an accronym for:
**bourne again shell**
73
what is the outcome of typing
**Cat** *file1 file2 file3 \> file4*
into a linux terminal
in a linux terminal:
this will concatenate each of the files given and then redirect the output to the file given
74
how can the operating system
## Footnote
**optimize pipelining**
The OS is also able to optimize this efficiently since the output of one command can be written to main memory and as soon as data starts to arrive the other command can start to consume it without the need for the first command to finish execution
75
what is the outcome of typing
**Find** */etc* **-name** *‘\*.conf’*
into a linux terminal
this will search in the /etc directory for any files that have a name ending with ‘.conf’
76
in a linux terminal:
this will print each of the given files to the terminal in the given order
what is the outcome of typing
**Cat** *file1 file2 file3*
into a linux terminal
77
achieving this is simply a case of entering the shell name into the termial
how do you switch between shells on a linux system
78
in a linux terminal:
this will copy the file *my-file* into the directory *my-directory*
what is the outcome of typing
**Cp** *my-file my\_directory*
into a linux terminal
79
in a linux or windows terminal what is the ( | ) used for
know as the pipeline. this allows you to redirect or 'pipe' the STDOUT (standard output stream) of one command to the STDIN (standard input stream) of another command
80
what is the outcme of typing
**Mkdir** *value*
into a linux terminal
in a linux terminal:
this will make a new directory with the name as the value given
81
what is the outcome of typing
**File** *filename*
into a linux terminal
in a linux terminal:
this will tell you the file type of the filename you have given
82
what is the syntax for
## Footnote
**grep**
the syntax is
**Grep** *‘string’* **options** *‘file or files’*
83
this will search in the /etc directory for any files that have a name ending with ‘.conf’
what is the outcome of typing
**Find** */etc* **-name** *‘\*.conf’*
into a linux terminal
84
this linux shell:
* uses similar loops, conditionals and expressions to the language C
give a point about the linux
## Footnote
**Csh (c shell)**
85
describe the linux
**su**
command
in linux this command is used when we would like to switch user accounts this includes logging in to the root account. this command is known as (switch user)
86
these are:
## Footnote
**.** - this points to the directory itself
**..** - this points to the parent directory
what are the 2
## Footnote
**hidden directories that every linux directory will have**
87
in a linux terminal:
this will rename the file *my-file* to *my-file2*
what is the outcome of typing
**mv** *my-file my-file2*
into a linux terminal
88
what is the outcome of typing
**Cd** *path*
into a linux terminal
in a linux terminal:
this will navigate you to the directory/path entered
89
describe the linux
**less**
command and a use case
This is a pager utility that allows you to view voluminous data either line by line or a page at a time.
If a command outputs a lot of data then piping it into this will help you read and navigate the text
90
linux commands are executed silently. meaning that unless there is an error or STDOUT then no feedback is given.
## Footnote
**what are 2 options that can provide feedback/security**
2 options in linux that provide this are
**-i** - known as interactive will prompt the user before each action
**-v** - known as verbose will print to screen confirmation messages
91
give a point about the linux
## Footnote
**Csh (c shell)**
this linux shell:
* uses similar loops, conditionals and expressions to the language C
92
in a windows and linux terminal what is the (\>) used for and 2 considerations to take into account before its use
this will redirect the STDOUT (standard output) of the command to a given file.
* If the file contains content it will be overwritten
* if the file does not exist it will be created
93
when using redirection or piping what are each of these aware of
1. the command
2. the shell/terminal
3. the OS
when this occurs:
1. **the command** - is not aware of anything being different or used
2. **the shell/terminal** - will interpret that this has been used and send the appropriate commands to the OS
3. **the OS** - will receive notification/commands from the shell and switch the STDOUT/STDIN appropriately
94
when a terminal is opened what are the default input and output streams configured by the operating system
when this occurs the operating system will set:
* the input stream as the keyboard
* the output stream as the terminal window
95
in a linux terminal:
this will remove the given directory but only ever if it is empty
what is the outcome of typing
**Rmdir** *directory*
into a linux terminal
96
how can we quickly view the available shells on a linux system via the terminal
this can be achieved by entering
cat /etc/shells
97
in a linux terminal:
this will suppresses the prompt confirming removal of write protected files and overrides the write protection. in turn deleting the file
what is the outcome of typing
**Rm** *filename* **-f**
into a linux terminal
98
this command will concatenate files and print on the standard output
give a description of the linux
**cat**
command
99
* **what is it** - This is a simple text editor that can be executed and ran inside the terminal
* **under what license is it released** - It is released under the GNU general public license meaning that end users can run, study, share and modify the software
* **what would be one appropriate situation for using this** - Linux has many configuration files written in plain text and using an editor such as this is the recommended approach to take when editing such files
give an answer to each of these points concerning
**nano**
* what is it
* under what license is it released
* what would be one appropriate situation for using this
100
This is a pager utility that allows you to view voluminous data either line by line or a page at a time.
If a command outputs a lot of data then piping it into this will help you read and navigate the text
describe the linux
**less**
command and a use case
101
how the linux cli operates
(come back to this at the end of the module)
• it prompts a user to type a command line
• it deals with editing within the line, accepting the line when Enter is pressed
• some special characters are picked out and handled specially, such as:
◦ quotation marks preserve spaces but are themselves stripped out
◦ \> and ◦ wildcards such as \* cause filenames to be expanded
• the completed command line is broken into pieces (tokens) by spaces
• the first token on the line is taken as the command
• if the command is built-in, then:
◦ the corresponding action is taken
• otherwise the file system is searched for a matching filename
• if a matching file is found, then:
◦ the type of file is determined
◦ if the file is a script, then:
– the script commands are interpreted recursively line by line
– until the end of the file
◦ if the file is an executable program:
– a system call obtains a chunk of memory from the memory management module
– a system call loads the contents of the program from the file system into that memory
– the remainder of the command-line arguments are copied to it
– a final system call is made to execute the program, relinquishing control of the processor through a context switch
– until the program ends and a context switch returns control to the shell
• else if no matching file is found, report an error
This process is then repeated.
102
describe the linux
**/etc/shells**
file
this is a file that contains the paths of available shells on the linux system
103
in a linux terminal:
this will move the file *my-file* into the directory *my\_directory*
what is the outcome of typing
**mv** *my-file my\_directory*
into a linux terminal
104
what does
**grep**
stand for
this is an abbreviation of
‘global regular expression print’
105
in a linux terminal:
this will open the file in the nano text editor ready for reading and editing
what is the outcome of typing
**Nano** *filename*
into a linux terminal
106
what is the outcome of typing
**Touch** *non-existing filename*
into a linux terminal
in a linux terminal:
will create a new file with the name of the given filename
107
what is the outcome of typing
**mv** *my-file my\_directory*
into a linux terminal
in a linux terminal:
this will move the file *my-file* into the directory *my\_directory*
108
in a linux terminal:
will create a new file with the name of the given filename
what is the outcome of typing
**Touch** *non-existing filename*
into a linux terminal
109
describe the linux
**/proc/cpuinfo**
file
this is a file that contains information about the systems processor
110
describe the linux
**/etc**
directory
this directory contains linux configuration files
111
what was the shell used on UNIX systems called and who created it
the shell used on this was named sh (bourne shell) as was written by stephen bourne
112
this is a set of standards and utilities maintained by IEEE that aims to maintain compatibility between operating systems. in turn meaning that an application can be run on either OS
The standards can define common APIs as well as how certain operating system tasks tasks should be handled.
Many OSs have some compliance with this
describe what
**POSIX (Portable Operating System Interface)**
is
113
this is an accronym for
## Footnote
**Portable Operating System Interface**
what does
POSIX
stand for
114
what is the outcome of typing
**Cd ..**
into a linux terminal
in a linux terminal:
this will take you back to the parent directory
115
give a description of the linux
**touch**
command
116
This linux command allows a single command to be executed with root privileges
describe the linux
**sudo**
command
117
in a linux terminal:
this prints the current working directory
what is the outcme of typing
**pwd**
into a linux terminal
118
what makes pipelining between commands possible
this is made possible because most commands will use text as thier input and output.
this means that commands can be used flexibly with each other since they are all using text format
119
this can be called by scripts on linux but is not strictly available on linux.
instead it is available to call but is symbolically linked to the dash shell
does the sh shell exist on linux
120
this linux shell:
* is compatible with bash but offers more customisation
* macOS has recently replaced bash with this shell
give 2 points about the linux:
## Footnote
**Zsh (z shell)**
121
give a description of the linux
**file**
command and how it works
this will determine the type of a file
it works by performing three test on the file to determine its type / content. The first test to complete successfully is output in the terminal
122
give three points about the linux:
**Bash (bourne again shell)**
this linux shell
* is a widely used shell in linux distributions
* maintains compatibility with the original sh shell
* maintains compatibility with the original sh shell
123
what does
**dash**
stand for
this is an accronym for
## Footnote
**debian almquist shell**
124
this will determine the type of a file
it works by performing three test on the file to determine its type / content. The first test to complete successfully is output in the terminal
give a description of the linux
**file**
command and how it works
125
what is the outcome of typing
**Ls -a**
into a linux terminal
in a linux terminal:
this will display all directories including any hidden ones
126
this is an accronym for
## Footnote
**debian almquist shell**
what does
**dash**
stand for
127
in a windows or linux terminal what does the (
this can be used to give STDIN (standard input) to a command from a file for example
128
in a linux terminal:
this will take you back to the parent directory
what is the outcome of typing
**Cd ..**
into a linux terminal
129
this will switch the shell to the root account and give the user full control of the system.
*root* can be omitted since linux will assume *root*
what is the outcome of typing
**Sudo su** *root*
into a linux terminal
130
in a linux terminal:
this will display all directories including any hidden ones
what is the outcome of typing
**Ls -a**
into a linux terminal
131
know as the pipeline. this allows you to redirect or 'pipe' the STDOUT (standard output stream) of one command to the STDIN (standard input stream) of another command
in a linux or windows terminal what is the ( | ) used for
132
describe the linux
**sudo**
command
This linux command allows a single command to be executed with root privileges
133
this can be achieved by entering
cat /etc/shells
how can we quickly view the available shells on a linux system via the terminal
134
what is the outcome of typing
**Date \>** *filename*
into a linux terminal
in a linux terminal:
this will redirect the output from the date command into the given filename, creating a new file if it does not exist
135
what are the 2
## Footnote
**hidden directories that every linux directory will have**
these are:
## Footnote
**.** - this points to the directory itself
**..** - this points to the parent directory
136
what is the outcome of typing
**Rmdir** *directory*
into a linux terminal
in a linux terminal:
this will remove the given directory but only ever if it is empty
137
this linux shell:
* is an extremely lightweight shell
* maintains compatibility strictly with the sh shell (can be used in place of the sh shell. this maintains compatibility with older scripts that may call sh)
give 2 points about the linux
## Footnote
**Dash (debian almquist shell)**
138
in a linux terminal:
this will concatenate each of the files given and then redirect the output to the file given
what is the outcome of typing
**Cat** *file1 file2 file3 \> file4*
into a linux terminal
