Udemy Linux Flashcards
(56 cards)
1
Q
Open Terminal
A
Ctrl + Alt + D
2
Q
Close Terminal
A
Ctrl + D
3
Q
echo
A
Prints out what you give it
4
Q
cal
A
Calendar
5
Q
date
A
today’s date & time
6
Q
clear
A
clear screen
7
Q
history
A
all previous commands
8
Q
to run command in history
A
! + line #
9
Q
!!
A
run most recent command
10
Q
history -c; history -w
A
clears history and makes changes permanent
11
Q
exit
A
terminal closes
12
Q
echo $PATH
A
current path
13
Q
which
A
which folder a command is in
14
Q
operand
A
input
15
Q
man
A
man pages
16
Q
man “-k” “which”
A
man page ; search ; for term “which” –> man (section number) “result title”
17
Q
>
A
standard output; #1; also 1>; will truncate
18
Q
> >
A
output; append file
19
Q
tty
A
see path of terminal
20
Q
<
A
standard INPUT
21
Q
cut
A
cuts files and returns specific columns (“fields”); –delimiter –> give it what divides the columns; –fields –> how many to output
22
Q
|
A
pipe data from standard input to next command for standard input
23
Q
tee
A
causes data to flow in two directions; saves to file as directed; allows file to be saved to continue piping
24
Q
xargs
A
(not all commands accept standard input, some only accept command line arguments) converts data from standard input and puts it into command line argument; can use command | xargs; command such as “echo”; command such as “cat” | xargs “rm”
25
rm
delete
26
.bash_aliases
file in home folder for aliases --> alias aliasName="command1 -options args | command 2 -options args ..." (make sure first command can be piped to, using xargs, if needed) --> restart terminal
27
pwd
print working directory; ~ --> home directory
28
absolute path
full path
29
ls -F
classiFy --> slash at the end is a directory (folder);
30
cd
change directory; ~(start at Home Directory)/; .=current directory; ..=parent folder or folder above
31
ls -a
show hidden files; hidden files start with .
32
touch
creates new empty files; touch // to create files inside directories / "folders"
33
create file with content inside
echo "" > ___fiel name_____.txt
34
mkdir
make directory; mkdir -p --> to create entire PATH; mkdir / --> will create folders inside folder
35
rm
remove file or directory
36
rm -r
delete recursively...delete the item and everything inside it; rm -ri (interactive, to have the r option ask for permission for each deletion)
37
rmdir
remove empty directory
38
cp
copy; cp -r --> copy the folder & everything inside (recursively)
39
locate
locate files; locate -i --> search in case insensitive way; locate --limit # --> limit to number of files; locate -S --> get information about database itself; locate -e --> check to see if files existed before reporting them / locate --existing; locate --follow / locate -L --> check links; (ONLY LISTS FILES)
40
updatedb
update database
41
find
DEFAULT BEHAVIOR: list every file & folder that is inside the current folder & lower down in the file system; always up-to-date (doesn't use database); use "/" to list all files & folders in system; can be used to list all contents in folders by using file path; file -maxdepth # to control number of levels find command searches; find . (current directory) -type f (for type: file) d (for type: directory/ "folder") --> can be combined with maxdepth option using maxdepth FIRST; find . -name "" --> place name in quotes; find . -maxdepth 10 -iname "?.TXT" --> ignore case in name search (case insensitive); sudo find / (starting at root directory, so use sudo command to avoid permission denied from getting access to files requiring administrative privileges) -type f -size +100k --> searches for files larger than 100 kilobytes in size; pipe output to | wc -l to count how many lines there are; chain together requirements -size +100k -size -5M (larger than 100 kilobytes but less than 5 megabytes, -o for the "or" option in-between sizes
42
-exec // -ok (OPTIONS)
execute OPTION; after command --> -exec __command to execute__ {} (every file) \; (to complete execution); using -ok will ask you each time if it is "ok" to do something
43
ctrl + L
clear the screen
44
cat
concatenate - "stick together"; or just read contents;
45
tac // rev (OPTIONS)
tac: reverse input; vertically -- keeps lines intact across columns; rev: reverses lines horizontally -- across the rows
46
less
paging program - page through large amounts of output
47
head
first # of lines; head -n #
48
sort
default: sort smallest first (a-z, 0-9); sort | tac (read backwards) OR sort -r (reverse) ; SORTING NUMBERS: sort using the value number give the "n" option --> sort -n (allows the sort command to sort numerically, instead of just by the digit); SORT FOR UNIQUE RESULTS: sort -q --> only get unique results; | sort -k (KEY DEFinition use for column) #column(+any other options, such as n, r, or u with no space...use h option to sort human-readable data -- h can NOT be used with n); M for month
49
grep
search for specific text; grep ___text_to_search_for____ ; use -c option for number of lines withs specific text (grep -c __texttosearch____ ; -i option for the search to be case insensitive; -v option finds all the lines that do NOT have a certain letter/term...grep -v / --> finds all files (not directories with / in folder name) v= invert search (do the opposite)
50
ls
ls -lF --> gives slash around directories and nothing for files
51
tar
compress file; tar -c(create a new archive)v(verbose - don't so this silently)f(accept files) ; tar -x(extract)vf; to create gzip file: tar -cvzf ; tar -cvjf; to extract gzip: tar -xvzf ; to extract bzip: tar -xvjf ;
52
gzip // bzip
gzip - faster but has less compression power; gzip (archive_name.tar) --> will see .gz file extension added; gunzip ("g unzip") to undo gzip
bzip - can compress smaller but requires more time; bzip2 --> will see bz2 file extension added (best for really large files); to undo --> bunzip2 ("b unzip 2")
53
zip
create zip file; zip .zip ; to undo unzip
54
bash script (Bourne-Again shell script)
nano .sh
#!(she-bang)/bin/bash(path to interpreter - to know words are commands) (verify with "which bash" at command prompt to retrieve interpreter's file path)
python3 to run python script ("which python3") /usr/bin/python3
bash to run bash script
55
add path to be found by running bash script in new directory
nano .bashrc
PATH="$PATH:$HOME/bin" if bin is created to hold bash scripts
PATH="$PATH:$HOME/"
new directory is now added to $PATH
*remember to make executable --> chmod +x *
56
cron utility
crontab -e --> open crontab editor (nano)
| ls -a from ~ --> hidden file with selected editor (.selected_editor) or command "select-editor"
