p1 working with the command line
DESCRIPTION
Python Working With the Command LineTRANSCRIPT
-
Manual pageshttp://linuxmanpages.com
man
man
man uses the less pager
Space one page forwardEsc + V one page backward/ searchQ quit
Manual sections
1 Excutable programs2 System calls3 Library calls4 Device files5 File formats6 Games7 Miscellaneous8 System administration commands9 Kernel routines
man passwd
man 5 passwd
passwd commandsection 1
/etc/passwd filesection 5
-
Create / Modify
Locate
View
Copy
Move
Rename
Archive
Compress
Delete
Linux treats almost everything as a file
regular files, directories, devices, sockets, pipes
touch, vi, nano, mkdir
less, ls
cp, dd
mv
tar, cpio
gzip, gunzip,bzip2
rm, rmdir find, locate
Basic file management
$ dd if=/dev/sda of=mbrsave bs=512 count=1
Create a backup copy of the MBR
-
General notions
Linux is case sensitive
Filename.txt filename.txt Special filenames. current directory.. parent directory
Filenames can contain any character.Filenames can be 255 characters long.
Wildcards* zero or more characters? only one character[] character set
Wildcard expansion = file globbing
Filenames should never contain wildcards: * ? \quotations: path separator: /
$ cd /usr/bin
$ pwd
$ cd .
$ pwd
$ cd ..
$ pwd
filesystem dependent
$ touch fileone filetwo
$ touch file*
$ rm file*
A wildcard stands in place of a group of characters
Replacing an wildcard with chars to obtainfile names in the current directory
-
Shell implementations
bash bsh tcsh csh ksh zsh
Bourne Again Shell
Bourne Shell
C Shell Korn Shell Z Shell
/bin/sh symbolic link to the default shell
Linux shell
Internal commands
echo
exec
time
exitlogout
cd cd ~
change directory
pwd print working directory
clear clear screen
replaces the shell
set
env export
ls
most common In linux
$ ls l /bin/sh
$ ls l /bin/*sh
some can also be external commands
-
Linux shell
Command Completion TAB
Command History
Ctrl + P
Ctrl + N
UpArrow
DownArrow
Ctrl + R reverse searchCtrl + S forward searchCtrl + G terminate search
History Search
~/.bash_history
history display all historyhistory c clear history
Bash configuration: /etc/profile ~/.bash_profile
Line editing
a command line in the shell
Ctrl+KDelCtrl+X; Bkspdelete
move Ctrl+ECtrl+Amove by one word
Ctrl+Left Ctrl+Right
$ less ~/.bash_history
-
read a variable
$ echo $HOSTNAME
$ env
displays all environment variables
set a variable
$ export HOSTNAME=lpic.credis.ro
set local variableexport to the environment
$ HOSTNAME=lpic.credis.ro
$ export HOSTNAME
When retrieving the value of a variable precede the variable name with a '$' character
Common environment variables: USER/USERNAME - Username of current user SHELL - Path to the current command shell PWD - Present Working Directory HOSTNAME - TCP/IP name of the computer HOME - Home directory of current user PATH - List of directories where executables are found PS1 - Default prompt in bash DISPLAY - The display used by X (:0.0) EDITOR - The default text editor
SHELLENV
CHILD SHELL
ENV
launchcopy
$ env
Launch a shell with a modified environment
Environment variablesmeans of passing named data
-
Streams, pipes & redirection
program stdin stdout
stderr
Standard Input Standard Output
Standard Error
< >>
2> 2>>
&>
here-is document
Discard errors $ command 2> /dev/null
tee [options] [files] Writes input to stdout and files-a, --append
program1 | program2
pipe
send output of program1 to input of program2
append
$ cat Some simple text
!