Linux Basic Learning-11th day (script loop, package management)

2016-08-16

Content of the lesson:

Shell Script Basics: Looping, for,while,until (not finished)

Package Management (not finished):

Software operating Environment

Package Basics

RPM Package Management

Loop execution

To run a code segment repeatedly multiple times

How many times to run repeatedly:

Number of cycles known beforehand

Number of cycles unknown beforehand

There are entry conditions and exit conditions

Loop Control statement:

Break :"lift end loop, loop will no longer execute" refers to the previous loop exit, and after exiting the command continues to execute, while exit exits the entire script

continue:"to end this cycle, and go to the next cycle" when the continue statement is encountered, the statement after the continue is no longer executed, directly ahead of the next round of circulation

For loop

For variable name in list;

Loop body

Done

List: Spaces separated by numbers, characters, files, and so on

Implementation mechanism:

Assigns the element in the list to the "variable name" in turn; The loop body is executed once each assignment; Until the elements in the list are exhausted, the loop ends

For example:

Write a script that prompts for the value of the positive integer n to calculate the sum of the 1+2+3+...N

#!/bin/bash #Version: 1.0 #Create time:2016-08-15 13:51:02 #Description: Write a script that prompts for the value of positive integer n, calculates the sum of 1+2+3+...N let sum=0 read-p "Input num:" num expr $NUM + 0 &>/dev/null [$? -ne 0] && echo "Please input Digitnum" && exit [$NUM-le 0] && echo ' Input the right NUM ' & amp;& Exit for I-in ' seq $NUM ' do sum=$ (($SUM + $I)) did echo "The sum is $SUM" unset SUM unset NUM

While loop:

While CONDITION; Do

Loop body

Done

Entry condition: condition is true;

Exit Condition: Condition is false

That is, when the loop body is really performing the loop body, the loop body is false is the exit loop body

For example:

Sum of all positive integers within 100

#!/bin/bash#version:1.0#create time:2016-08-15 14:36:00#description: Sum of all positive integers within 100 let sum=0let num=1while [$NUM-le Do sum=$ (($SUM + $NUM)) num=$ (($NUM + 1)) Doneecho "1+2+...+100= $SUM"

Until cycle

Until CONDITION; Do

Loop body

Done

Entry condition: CONDITION is False

Exit Condition: CONDITION is True

"That is, when the loop body is really the loop body, the loop body is false is to exit the loop body, in contrast to the while loop

Package Management:

Software operating Environment

Program Source--preprocessing----compile-to-link

Note content is removed during preprocessing

Abi:application Binary Interface

Windows is incompatible with Linux, such as the LS command no longer works with Windows because Uwindows and Linux have different ABI interfaces

Package Manager:

Components of a binary application:

binary files, library files, configuration files, Help files

Package Manager:

Debian:deb file, dpkg Package Manager

redhat:rpm files, RPM Package Manager, SuSE series also use RPM Package Manager

Rpm:redhatpackage Manager (initial)

RPM Package Manager(industry standard, similar to GNU)

Package naming

Source code: NAME-VERSION.TAR.GZ|BZ2|XZ

VERSION:major.minor.release

RPM Package Naming method:

name-version-release.arch.rpm

Example: bash-4.2.46-19.el7.x86_64.rpm

VERSION:major.minor.release (that is, how the source code is named)

Release:release. OS

OS:EL7, referring to the RHEL7 version.

Common arch:

X86:i386, i486, i586, i686 (32-bit platform)

X86_64:x64, x86_64, AMD64 (64-bit platform)

Powerpc:ppc

Platform agnostic: Noarch

Package: One RPM package contains multiple files

APPLICATION-VERSION-ARCH.RPM: Main Package

APPLICATION-DEVEL-VERSION-ARCH.RPM Development Sub-package

application-utils-version-arhc.rpm Other sub-packages

application-libs-version-arhc.rpm Other sub-packages

Between packages: There may be dependencies, or even cyclic dependencies

To resolve the dependency package management tool:

YUM:RPM Package Manager Front-end tools

Apt-get:deb Package Manager Front End Tool

Since a binary executable package consists of binary files, library files, Help files, and configuration files, each package file includes:

1. package file composition (unique for each package)

The files in the RPM package

RPM metadata, such as name, version, dependency, description, etc.

Scripts to run when installing or uninstalling

2. Database (public)

Package Name and version

Dependent relationships

Function description

File path and checksum information generated after package installation

How to manage Packages:

Using Package Manager: RPM

Using the front end tool: Yum, DNF

RPM:

1. Installation

RPM {-i|--install} [install-options] package_file ...

-V: Show details

-H: Show Progress in #

[Install-options]:

--test: Test installation, but do not actually perform installation; dry run mode

--nodeps: Ignoring dependencies

--replacepkgs| Replacefiles

--nosignature: Does not check the legitimacy of the source

--nodigest: Package integrity is not checked

--noscipts: Do not execute Package script fragment

%pre: Pre-installation;--nopre

%post: Post-installation script;--nopost

%preun: Unloading the forefoot;--nopreun

%postun: Post-uninstall script;--nopostun

2. Upgrade

RPM {-u|--upgrade} [install-options] package_file ...

RPM {-f|--freshen} [install-options] package_file ...

Upgrade: Install an older version of the package, then "Upgrade"

If there is no legacy package, the Install

Freshen: Install an older version of the package, then "Upgrade"

If the legacy package does not exist, the upgrade operation is not performed

RPM-UVH Package_file ...

RPM-FVH Package_file ...

--oldpackage: Downgrade

--force: Forced escalation

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Linux Basic Learning-11th day (script loop, package management)