#####Shell, Basic linux Command#####
1.tty - reveals the current terminal
2.whoami - reveals the currently logged-in user
3.which - reveals where in the search path a program is located
4.echo - prints to the screen
a. echo $PATH - prints out the current path to STDOUT
b. echo $PWD - dumps the contents of the $PWD variable
c. echo $OLDPWD - dumps the
5. set - prints and optionally sets shell variables
6. clear - clears the screens or terminal
7. reset - clears the screen buffer
8. history - reveal command history
a. !600 - executes the 600th command in our history
b. command histroy is maintained on a per-user basis via:~/.bash_history
c. ~ - users's $HOME directory in the BASH shell
9. pwd - prints the working directory
10. cd - changes directory to desired directory
a. 'cd ' with no options changes to the $HOME drectory
b. 'cd ~' changes to the $HOME directory
c. 'cd /' changes to root directory
d. 'cd Desktop/' changes to the relative directory
e. 'cd..' 'cd ../..' chages one-level/ two-levels up in the directory tree\
11. Arrow ( up/down) keys
12. Bash supports tab completions
a. type unique characters in the command and press 'Tab' key
13. copy and paste in GNOME terminal windows using:
a. left button to block
b. right button to paste OR Ctrl-Shift-v to past
14.ls - lists directories
a. ls / - lists the contens of the '/' mount point
b. 'ls -l' - lists the contents of a direcotry in long format
c. 'ls -ld' - lists the directory properties rather than the contents
d. 'ls -ltr' sorts chronologically from older to newer ( bottom )
e. 'ls -help'
f. 'ls -a' - reveal hiden files
Note: files/directories prefixed with '.' are hidden
15. cat - catenates files
a. can dumps multiple files to STDOUT
16. mkdir - creates a new directory
17. cp - copies files
By default, 'cp' does NOT preserve the original modification time
18. mv - moves files
19. rm - remove files/directories
a. 'rm -rf' - removes recursively and enforces
20. touch - creaes blank files / updates timestamp
a. touch test.txt - will create a 0 file if it didn't exist
Will update timestamp if it does exist
b. touch -t 200901091530 test.txt - will change timestamp
21. stat - reveals statistics of files
22. find - finds files using search patterns
a. find / -name 'fstab*'
Note: 'find' can search for fields returned by the 'stat' command
23. alias - returnsds/sets aliansed for commands
###Linux Redirection & Pipes###
Features:
1. Ability to control input and output
Input redirection '<'
Input redirection:
1. cat < 123.tst
Note: Use input direction when program does NOT default to file
Output redirection '>'
1. cat 123.txt > onetwothree.txt
Note: Default nature is to:
a. Clobber the target file
b. Populate with information from input stream
Append redirection '>>'
1. cat 123.txt >> numbers.txt - creates 'numbers.txt' if it doesn't exist,
or appends if it does
Pipes '|'
Features: Connects the output stream of one command to the input stream of a subsequent command
###Command Chaining###
Features:
1. Permits the execution of multiple commands in sequence
2. Also permits execution based on the success or failure of a previous command
Previous command
1. cat 123.txt ; ls -l - this runs first command, then second command without regards for exit status of the first command
2. cat 123.txt && ls -l - This will run second command, if the first command is successful
3. cat 123.txt || ls -l - This will run second command, if the first command failed.
24. more | less - paginators, which display text on-page at a time
1. more /etc/
25. seq - echoes a sequence of numbers
a. swq 1000 > 1000.txt
b. seq 5 5 100 > 55.txt
26. su - switches users
a. su - with on option will attempt to login to root
27. head - displays opening lines of the text files
28. tail - displays the closing lines of text files
29. wc - counts words and optionally lines of the text files
30. file - determines file type
a file /var/log/messages
