Ubuntu Linux Toolbox 1000+ Commands for Ubuntu and Debian Power Users phần 10 pps

with l, w, or $ to copy yank the currentletter, word, or end of linefrom cursor Shift+y Yank current line p Pastes cut or yanked text after cursor Shift+p Pastes cut or yanked text befor

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Table A-2: Commands for Changing Text (continued)

Table A-3 contains keys you type to delete or paste text

Table A-3: Commands for Deleting and Pasting Text

Using Miscellaneous Commands

Table A-4 shows a few miscellaneous, but important, commands you should know

x Delete text under cursor Shift+x Delete text to left of

cursor

d? Replace ? with l, w, $, or

d to cut the current letter,word, or end of line from cursor or entire line

Shift+d Cut from cursor to end

of line

y? Replace ? with l, w, or $ to

copy (yank) the currentletter, word, or end of linefrom cursor

Shift+y Yank current line

p Pastes cut or yanked text

after cursor

Shift+p Pastes cut or yanked

text before cursor

o Open a new line below

current line to begin typing

Shift+o Open a new line above

current line to begintyping

s Erase current character

and replace with new text

Shift+s Erase current line and

enter new text

c? Replace ? with l, w, $, or c

to change the current letter,word, end of line, or line

Shift+c Erase from cursor to

end of line and enternew text

r Replace current character

with the next one you type

Shift+r Overwrite as you type

from current charactergoing forward

293 Appendix A: Using vi or Vim Editors

82935bapp01.qxd:LinuxToolbox 10/29/07 1:20 PM Page 293

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Table A-4: Miscellaneous Commands

Modifying Commands with Numbers

Nearly every command described so far can be modified with a number In otherwords, instead of deleting a word, replacing a letter, or changing a line, you can deletesix words, replace 12 letters, and change nine lines Table A-5 shows some examples

Table A-5: Modifying Commands with Numbers

From these examples, you can see that most vi keystrokes for changing text, deletingtext, or moving around in the file can be modified using numbers

Command Result

7cw Erase the next seven words and replace them with text you type

5, Shift+d Cut the next five lines (including the current line)

3p Paste the previously deleted text three times after the current cursor9db Cut the nine words before the current cursor

10j Move the cursor down ten lines

y2) Copy (yank) text from cursor to end of next two sentences

5, Ctrl+f Move forward five pages

6, Shift+j Join the next six lines

u Type u to undo the previous change Multiple u commands will step back

to undo multiple changes

Typing a period (.) will repeat the previous command So, if you deleted a

line, replaced a word, changed four letters, and so on, the same commandwill be done wherever the cursor is currently located (Entering input modeagain resets it.)

Shift+j Join the current line with the next line

Esc If you didn’t catch this earlier, the Esc key returns you from an input mode

back to command mode This is one of the keys you will use most often

294

Appendix A: Using vi or Vim Editors

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Using Ex Commands

The vi editor was originally built on an editor called Ex Some of the vi commands

you’ve seen so far start with a semicolon and are known as Ex commands To enter

Ex commands, start from normal mode and type a colon (:) This switches you tocommand line mode In this mode, you can use the Tab key to complete your com-mand or file name, and the arrow keys to navigate your command history, as youwould in a bash shell When you press Enter at the end of your command, you arereturned to normal mode

Table A-6 shows some examples of Ex commands

Table A-6: Ex Command Examples

From the exprompt you can also see and change settings related to your vi sessionusing the setcommand Table A-7 shows some examples

:5,10w abc.txt Write lines 5 through 10 to the file abc.txt

:e abc.txt Leave the current file and begin editing the file abc.txt.:.r def.txt Read the contents of def.txt into the file below the

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Table A-7: set Commands in ex Mode

Working in Visual Mode

The Vim editor provides a more intuitive means of selecting text called visual mode To

begin visual mode, move the cursor to the first character of the text you want to selectand press the vkey You will see that you are in visual mode because the following textappears at the bottom of the screen:

VISUAL

At this point, you can use any of your cursor movement keys (arrow keys, Page Down,End, and so on) to move the cursor to the end of the text you want to select As the pageand cursor move, you will see text being highlighted When all the text you want toselect is highlighted, you can press keys to act on that text For example, ddeletes thetext, clets you change the selected text, :w /tmp/test.txtsaves selected text to a file,and so on

:set all List all settings

:set List only those settings that have changed from the default

:set number Have line numbers appear left of each line (Use set nonu to unset.):set ai Sets autoindent, so opening a new line follows the previous indent.:set ic Sets ignore case, so text searches will match regardless of case

:set list Show $ for end of lines and ^I for tabs

:set wm Causes vi to add line breaks between words near the end of a line

296

Appendix A: Using vi or Vim Editors

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Shell Special Characters and Variables

Ubuntu provides bash as the default shell

Chapter 3 helps you become comfortable working

in the shell This appendix provides a reference ofthe numerous characters and variables that havespecial meaning to the bash shell Many of thoseelements are referenced in Table B-1 (Shell SpecialCharacters) and Table B-2 (Shell Variables)

Using Special Shell Characters

You can use special characters from the shell to match multiple files, savesome keystrokes, or perform special operations Table B-1 shows someshell special characters you may find useful

Table B-1: Shell Special Characters

Continued

Character Description

* Match any string of characters

? Match any one character

[ ] Match any character enclosed in the braces

‘ … ‘ Remove special meaning of characters between quotes

Variables are not expanded

“ … “ Same as simple quotes except for the escape characters

($ ` and \) that preserve their special meaning

\ Escape character to remove the special meaning of the

character that follows

IN THIS APPENDIX

Using special shellcharactersUsing shell variables82935bapp02.qxd:LinuxToolbox 10/29/07 1:37 PM Page 297

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Table B-1: Shell Special Characters (continued)

Using Shell Variables

You identify a string of characters as a parameter (variable) by placing a $in front of

it (as in $HOME) Shell environment variables can hold information that is used by theshell itself, as well as by commands you run from the shell Not all environment vari-ables will be populated by default Some of these variables you can change (such as thedefault printer in $PRINTERor your command prompt in $PS1) Others are managed

by the shell (such as $OLDPWD) Table B-2 contains a list of many useful shell variables

Character Description

~ Refers to the $HOME directory

~+ Value of the shell variable PWD (working directory)

~- Refers to the previous working directory

Refers to the current working directory

Refers to the directory above the current directory Can be used

repeatedly to reference several directories up

$param Used to expand a shell variable parameter

cmd1> Redirects standard output from command

cmd1< Redirects standard input to command

cmd1>> Appends standard output to file from command, without erasing its

current contents

cmd1|cmd2 Pipes the output of one command to the input of the next

cmd& Runs the command in the background

cmd1&&cmd2 Runs first command, then if it returns a zero exit status, runs the

second command

cmd1||cmd2 Runs first command, then if it returns a non-zero exit status, runs

the second command

cmd1 ;cmd2 Runs the first command and when it completes, runs the second

command

298

Appendix B: Shell Special Characters and Variables

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Table B-2: Shell Variables

Continued

Shell Variable Description

BASH Shows path name of the bash command (/bin/bash)

BASH_COMMAND The command that is being executed at the moment

BASH_VERSION The version number of the bash command

COLORS Path to the configuration file for ls colors

COLUMNS The width of the terminal line (in characters)

DISPLAY Identifies the X display where commands launched from the

current shell will be displayed (such as :0.0)

EUID Effective user ID number of the current user It is based on the user

entry in /etc/passwd for the user that is logged in

FCEDIT Determines the text editor used by the fc command to edit

historycommands The vi command is used by default

GROUPS Lists groups of which the current user is a member

HISTCMD Shows the current command’s history number

HISTFILE Shows the location of your history file (usually located at

$HOME/.bash_history)

HISTFILESIZE Total number of history entries that will be stored (default, 1000)

Older commands are discarded after this number is reached.HISTCMD The number of the current command in the history list

HOME Location of the current user’s home directory Typing the cd

com-mand with no options returns the shell to the home directory.HOSTNAME The current machine’s host name

HOSTTYPE Contains the computer architecture on which the Linux system is

running (i386, i486, i586, i686, x86_64, ppc, or ppc64)

LESSOPEN Set to a command that converts content other than plain text

(images, RPMs, zip files, and so on) so it can be piped through thelesscommand

LINES Sets the number of lines in the current terminal

299 Appendix B: Shell Special Characters and Variables

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Table B-2: Shell Variables (continued)

Shell Variable Description

LOGNAME Holds the name of the current user

LS_COLORS Maps colors to file extensions to indicate the colors the ls

com-mand displays when encountering those file types

MACHTYPE Displays information about the machine architecture, company, and

operating system (such as i686-redhat-linux-gnu)MAIL Indicates the location of your mailbox file (typically the user name

in the /var/spool/mail directory)

MAILCHECK Checks for mail in the number of seconds specified (default is 60).OLDPWD Directory that was the working directory before changing to the

current working directory

OSTYPE Name identifying the current operating system (such as linux or

linux-gnu)PATH Colon-separated list of directories used to locate commands that you

type (/bin, /usr/bin, and $HOME/bin are usually in the PATH).PPID Process ID of the command that started the current shell

PRINTER Sets the default printer, which is used by printing commands such

as lpr and lpq

PROMPT_COMMAND Set to a command name to run that command each time before your

shell prompt is displayed (For example, PROMPT_COMMAND=lslists commands in the current directory before showing the prompt).PS1 Sets the shell prompt Items in the prompt can include date, time,

user name, hostname, and others Additional prompts can be setwith PS2, PS3, and so on

PWD The directory assigned as your current directory

RANDOM Accessing this variable generates a random number between 0 and

32767

SECONDS The number of seconds since the shell was started

SHELL Contains the full path to the current shell

SHELLOPTS Lists enabled shell options (those set to on)

300

Appendix B: Shell Special Characters and Variables

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Getting Information from /proc

Originally intended to be a location for storinginformation used by running processes, the /procfile system eventually became the primary locationfor storing all kinds of information used by theLinux kernel Despite the emergence of /systoprovide a more orderly framework for kernel infor-mation, many Linux utilities still gather and pres-ent data about your running system from /proc

If you are someone who prefers to cut out the middleman, you can bypassutilities that read /procfiles and read (and sometimes even write to) /procfiles directly By checking /proc, you can find out the state of processes,hardware devices, kernel subsystems, and other attributes of Linux

Viewing /proc information

Checking out information in files from the /procdirectory can be done

by using a simple catcommand In /proc, there is a separate directoryfor each running process (named by its process ID) that contains informa-tion about the process There are also /procfiles that contain data for allkinds of other things, such as your computer’s CPU, memory usage, soft-ware versions, disk partitions, and so on

The following examples describe some of the information you can getfrom your Linux system’s /procdirectory:

root=UUID=db2dac48-a62e-4dbe-9529-e88a57b15bac ro quiet splash

Processor : 0vendor_id : GenuineIntelcpu family : 6

model : 8

IN THIS APPENDIX

Viewing /proc informationChanging /proc information variables82935bapp03.qxd:Toolbox 10/29/07 1:48 PM Page 301

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model name : Pentium III (Coppermine)

stepping : 3

cpu MHz : 648.045

cache size : 256 KB

In the example above, the MHz speed may be well below your actual system speed if

a CPU governor such as cpuspeedis running

$ cat /proc/devices Shows existing character and block devices

in progress, number of milliseconds spent doing input/output, and weighted number

of milliseconds spend doing input/output Fields for a particular partition show (fromleft to right): number of reads issued, number of sectors read, number of writes issued,and number of sectors written

nodev sysfs nodev means type is not currently used by any device

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$ cat /proc/interrupts View IRQ channel assignments

CPU00: 198380901 XT-PIC-XT timer1: 28189 XT-PIC-XT i80422: 0 XT-PIC-XT cascade6: 3770197 XT-PIC-XT Ensoniq AudioPCI7: 660 XT-PIC-XT parport0

$ cat /proc/iomem Show physical memory addresses

00000000-0009fbff : System RAM

00000000-00000000 : Crash kernel0009fc00-0009ffff : reserved

000a0000-000bffff : Video RAM area

$ cat /proc/loadavg Shows 1, 5, and 15 minute load averages,

1.77 0.56 0.19 2/247 1869 running processes/total and highest PID

229 fuse registered with misc major device (10)

63 device-mapper

175 agpgart

144 nvram

nls_utf8 6209 1 - Live 0xd0c59000 instances loaded, dependencies

cifs 213301 0 - Live 0xd0e3b000 load state, and kernel memory

303 Appendix C: Getting Information from /proc

82935bapp03.qxd:Toolbox 10/29/07 1:21 PM Page 303

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none /sys sysfs rw,nosuid,nodev,noexec 0 0

none /proc proc rw,nosuid,nodev,noexec 0 0

udev /dev tmpfs rw 0 0

/dev/disk/by-uuid/db2dac48-a62e-4dbe-9529-e88a57b15bac / ext3 rw,data=ordered 0 0

/dev/disk/by-uuid/db2dac48-a62e-4dbe-9529-e88a57b15bac /dev/.static/dev ext3 rw,data=ordered 0 0

tmpfs /var/run tmpfs rw,nosuid,nodev,noexec 0 0

tmpfs /var/lock tmpfs rw,nosuid,nodev,noexec 0 0

tmpfs /lib/modules/2.6.20-16-generic/volatile tmpfs rw 0 0

tmpfs /dev/shm tmpfs rw 0 0

devpts /dev/pts devpts rw 0 0

usbfs /dev/bus/usb/.usbfs usbfs rw 0 0

udev /proc/bus/usb tmpfs rw 0 0

usbfs /proc/bus/usb/.usbfs usbfs rw 0 0

fusectl /sys/fs/fuse/connections fusectl rw 0 0

rpc_pipefs /var/lib/nfs/rpc_pipefs rpc_pipefs rw 0 0

binfmt_misc /proc/sys/fs/binfmt_misc binfmt_misc rw 0 0

major minor #blocks name

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The /proc/mdstatfile contains detailed status information on your software RAIDdevices, if you have set up such a software RAID device In this example, md0is aRAID1 (mirror) composed of the /dev/sdb1and /dev/sda1partitions On the fol-lowing line, there is one Ufor each healthy RAID member If you lose a drive, theoutput would appear as [U_].

$ cat /proc/stat Shows kernel stats since system boot

Filename Type Size Used Priority

/dev/sda2 partition 1020088 201124 -1

2300251.03 2261855.31

$ cat /proc/version List kernel version and related compiler

Linux version 2.6.20-16-generic (root@terranova) (gcc version 4.1.2 (Ubuntu 4.1.2-0ubuntu4)) #2 SMP Fri Aug 31 00:55:27 UTC 2007

Changing /proc information

On some versions of Linux, some values in the /proc/sysdirectory can actually

be changed on the fly For /proc/sysfiles that accept binary values (0 disabled or 1enabled) people would often simply echo a value to any files they wanted to change.Ubuntu does not allow this feature, though

The preferred method of changing /proc/sysinformation on the fly is using thesysctlcommand To change those settings on a more permanent basis, you shouldadd entries to the /etc/sysctl.conffile Here are some examples of the sysctlcommand:

See Chapter 10 as well as the sysctland sysctl.confman pages for further information

305 Appendix C: Getting Information from /proc

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Index Index

A

Address Resolution Protocol (ARP)

delete entry from cache, 228

disable name resolution, 228

entries, listing, 228

functions of, 228

static entries, adding to cache, 228

Adept, as Kubuntu feature, 2

Ad-Hoc mode, wireless connections, 222

administrative commands, man pages, 13

Advanced Linux Sound Architecture

define for bash session, 58

removing from bash session, 58

alphanumeric order, sort based on, 101

alsamixercommand, audio levels,

adjusting, 111

Alternate Desktop CD option, 18

anacron facility, 185

append to file, shell, 55

aproposcommand, man pages, searching,

9, 12

APT (Advanced Package Tool), 3, 25–31

cache clean-up with, 30–31

command line reference for, 25

installing packages with, 28–29

new software, query for, 28

removing packages with, 30repository/third-party signature key,adding, 27–29

software package installation, 21updates, 29–30

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