Linux Punch 3

Review:

Shell:type,which, environment variable path

[Email protected] ~]# echo $PATH

/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

Reference variable: ${variable name}

Variable: A named memory space that can be found directly in the shell

Use Help:

# Help Command

# command--help

# Mans [Section] command

1-8:1, 8, 5

1 g: Turn to the first line

G: Turn to the last line

Q

# info

# application comes with documentation: README, INSTALL,/usr/share/doc

# google

# official documentation of the release version

Use format for commands:

Command option Parameters

Export lang=en

New courses:

Commands for the System Management class:

shutdown [option] ... Time

-R: Restart

-H: Shutdown

-C: Cancel restart or shutdown command shutdown-c

Time Format:

Now

+#: #分钟以后

hh:mm shutdown at a specified time

Reboot

Halt-p

Poweroff

Date Time Management class command:

Date (System clock), Hwclock (Hardware clock)

# date

# Date MMDDHHMM[CC]YY.SS Month day year. seconds

[[Email protected] ~]# date 100711032015.22

Wed OCT 7 11:03:22 EDT 2015

Use this to set the system time directly

# date [+format]

%Y: four-bit year

%y:2 bit Year

%m: Month

%M: Min

%d: Day

%H: Month

%H: When

%s: Seconds

%d: Date

%F: Date

[Email protected] ~]# date +%f

2015-10-07

[Email protected] ~]# date +%y-%m-%d

2015-10-07

[Email protected] ~]# date +%f-%h-%m-%s

2015-10-07-11-31-04

The time is all uppercase, and the date is lowercase.

Unix: 1970-01-01 00:00:00

%s:timestamp

[Email protected] ~]# date +%s

1444232025

#cal View Calendars

Linux has two clocks:

Hardware clock: used when starting up

Software clock: Read hardware clock at boot time

Hc

Sys

Hwclock can set two clock synchronization:

-S: Based on hardware clock,--hctosys

-W: Based on the system clock,--SYSTOHC

[Email protected] ~]# Hwclock;d ate

Sat Oct 3 12:02:47 2015-0.787231 seconds

Wed OCT 7 11:12:49 EDT 2015

[Email protected] ~]# hwclock-w

[Email protected] ~]# Hwclock;d ate

Wed Oct 7 11:13:04 2015-0.424462 seconds

Wed OCT 7 11:13:03 EDT 2015

Summary: Man, info, help, date, Hwclock, Cal, shutdown, reboot, Halt, Poweroff, type, CD, which, DirName, BaseName, who, which, Whatis, Makewhatis, Echo, hash, TTY

/: Root partition, root file system, ROOTFS, associated partition for mount and unload operations.

Commands for the file and directory management classes:

Current directory: Working directory

Home directory, home directory CD ~ can be implemented back home directory

Shell command-line expansion: Ability to change a special character to another character;

~: Specify the user's home directory;

{,}: expand to multiple entries;

X/{a,b} = x/a, x/b

Directory:

CD ~[username] Back to a user's directory, only Root can operate

CD-: Go back to your last directory;

/usr/share/doc/yum-3.2.1

CD-=/usr/share/doc

CD-=/usr/share/doc/yum-3.2.1

CD-

Path:

In the relative path:

.: Current Directory

..: Parent Directory

Pwd:print working Directory

mkdir: Creating a Directory

-P: Create parent directory first;

-V: Displays detailed information;

mkdir/a/b/c/d

x/a, x/b, x/a/m, x/a/n

MKDIR-PV x/{a/{m,n},b} Create parent directory at the same time

[[email protected] ~]# MKDIR-PV x/{a/{m,n},b}

mkdir:created directory ' x '

mkdir:created directory ' x/a '

mkdir:created directory ' x/a/m '

mkdir:created directory ' x/a/n '

mkdir:created directory ' x/b '

A_c, A_d, B_c, B_d

mkdir a_c a_d B_c b_d

mkdir {A,b}_{c,d}

(x+y) (m+n) = xm + xn + ym + yn

RmDir: Delete empty directory is deleted directory is not a file, if there are files under the directory, you cannot delete

Rmdir-p/x/c/v refers to the deletion of V, but if the first line of only son is empty, it is all deleted.

Exercise: Creating/tmp/mylinux/usr/local/bin,/tmp/mylinux/usr/local/sbin,/tmp/mylinux/etc/sysconfig,/TMP/MYLINUX/ETC/INIT.D ,/tmp/mylinux/bin,/tmp/mylinux/sbin

# Mkdir-pv/tmp/mylinux/{usr/local/{bin,sbin},etc/{sysconfig,init.d},bin,sbin}

Execution result of the command:

mkdir:created directory '/tmp/mylinux '

mkdir:created directory '/tmp/mylinux/usr '

mkdir:created directory '/tmp/mylinux/usr/local '

mkdir:created directory '/tmp/mylinux/usr/local/bin '

mkdir:created directory '/tmp/mylinux/usr/local/sbin '

mkdir:created directory '/tmp/mylinux/etc '

mkdir:created directory '/tmp/mylinux/etc/sysconfig '

mkdir:created directory '/TMP/MYLINUX/ETC/INIT.D '

mkdir:created directory '/tmp/mylinux/bin '

mkdir:created directory '/tmp/mylinux/sbin '

Exercise: Create/tmp/a B

[[email protected] tmp]# mkdir ' A B ' can also use double quotes, and underline

[[email protected] tmp]# ls

A b yum.log

References in the shell:

': Strong reference (what value is entered to show what value), variable substitution does not

"": weak reference, ability to perform variable substitution

"(Anti-quote): command substitution, the execution result of the reference command; another symbol of the command substitution: $ (command);

Inside the inverted quote is the instruction

[Email protected] ~]# echo "Time is ' date +%t '"

Time is 12:37:06

Inverted quotes in double quotes

Variable substitution: ${variable name} gets the value corresponding to the variable name

Echo

Exercise: Create a directory with the current time command, such as 2014-02-11-16-25-20;

# mkdir ' Date +%f-%h-%m-%s '

# mkdir $ (date +%f-%h-%m-%s)

Practice:

1. Create/TMP/ETC/RC.D,/TMP/ETC/RC.D/INIT.D,/TMP/ETC/RC.D/RC0.D,/tmp/etc/sysconfig,/tmp/etc/pam,/tmp/etc/ yum.repos.d/

MKDIR-PV ETC/{RC.D/{INIT.D,RC0.D},SYSCONFIG,PAM,YUM.REPOS.D}

2. Create/TMP/ETC/RC.D,/TMP/ETC/RC.D/INIT.D,/TMP/ETC/RC.D/RC0.D,/tmp/etc/sysconfig,/tmp/etc/pam,/tmp/etc/ yum.repos.d/,/tmp/usr,/tmp/usr/share,/tmp/usr/share/doc,/tmp/usr/share/man,/tmp/usr/bin,/tmp/usr/sbin,/TMP/USR /lib,/tmp/usr/lib64

Command summary: PWD, mkdir, rmdir

Shell's three characteristics: command history

A list of commands that have been executed by bash in the past;

The current shell process is saved in a buffer;

The commands in the buffer are saved to the file when the shell exits. Bash_history

Use the UP and DOWN ARROW keys to look at previously executed commands;

History shortcut (previously entered instruction): The following direct input can be

!#: #为命令历史列表中的命令编号; can execute the # command;

!: Executes the previous command;

!-#: Executes the penultimate # command in the command history list;

!string: Executes the last command in the command history list that starts with string;

!$: Refers to the last argument of the last command; ESC.

History

-C: Empty list

-D #: Delete the specified history command

-A: Append the current session's command history to the history file;

-N: Append the history file's instructions to the list

-A: Append the list's instructions to the history file

Command history-related environment variables:

Histsize: The number of commands that can be saved in the list in the command history; Echo $HISTSIZE

Histfile: Command history file, location of file

Histfilesize: The number of commands the command history file can hold;

[Email protected] ~]# echo $HISTFILE

/root/.bash_history

[Email protected] ~]# echo $HISTFILESIZE

1000

Histcontrol: Control the generation of command history; The following 3 are the values that can be assigned to a Histcontrol

Ignoredups: Ignore record duplicate command, repeat the same command for consecutive;

Ignorespace: Do not log commands that begin with a blank character;

Ignoreboth: Both of the above characteristics;

Add: Another feature of the Linux file system: Files that start with a dot are hidden files; Ls-a

Variables in the shell are assigned values:

Variable name = value

Note: Variables cannot be used when assigning values;

Variable names can contain only letters, numbers, and underscores, and cannot start with a number;

Variable names are case-sensitive;

FHS: File Hierarchy Standard

/bin: All users can execute programs, executable programs, operating system to start their own operation will be used by the program

/sbin: An administrator executable program that executes programs that the operating system uses to start its own operation

/usr/bin, in order to ensure that the operating system has basic functions, the basic operating procedures provided

/usr/sbin, in order to ensure that the operating system has basic functions, the basic operating procedures provided

/usr/local/bin, which is used to install third-party programs, such as Oracle,mysql

/usr/local/sbin, which is used to install third-party programs

/boot: Storage System Boot file: Kernel, Ramfs file, bootloader (GRUB);

/dev: Device file storage directory, is a type of special files;

/etc: the directory where the configuration files are stored;

/etc/sysconfig:

/ETC/INIT.D: System service scripts, and RunLevel-related

/home: A normal user, by default, has a directory with the same name as the user's family directory.

/root: Administrator's home directory;

/lib,/lib64: library files, here are the standard library files,/bin and/sbin and/usr/bin and/usr/sbin programs require the library files are here, and/usr/local/bin is not, it has its own library file

/media: A dedicated mount location, typically used to mount a portable device, such as inserting a USB stick, whose files are mounted under media.

/MNT: Dedicated mount location, mount additional storage devices, such as adding a new hard drive

/misc: Alternate Directory

/OPT: Alternate directory, but usually used to install third-party software;

/proc: Pseudo-file system, kernel parameter mapping, which shows the kernel running state parameters, a shutdown is not, performance as a file: file name is the parameter name, content is value.

/sys: Pseudo file system, system-level parameters for configuring peripheral devices, hardware parameters, performance as files: File name is parameter name, content is value.

/SRV: Provide data storage location for service;

/tmp: temporary file system;

/usr: Shared file s:shared (files can be used on all Linux systems that follow the FSH specification), r:readonly (Read only)

/usr/include: Header File

/var: files that are frequently changed

/var/log Log

/var/lock lock file, service

/var/run

/var/cache

Normal users can create their own files only with TMP and home directories.

Linux Punch 3