• linux 使用大全

    文章目录

    Part one - 基础命令

    1、命令

    1. date
    2. cal -calendar
    3. df -current amount of free space on your disk drives
    4. free -display the amount of free memory
    5. exit -closing the terminal emulator window

    2、Navigation(导航)

    1. pwd - Print name of current working directory
    2. cd - Change directory
    3. ls - List directory contents
    4. file – Determine file type
    5. less – View file contents（和cat的区别？参考）

    4 Manipulating Files And Directories(文件与目录)

    1. cp #如果文件已经存在，直接覆盖，没有提示，要提示用-i
    2. mv
    3. mkdir
    4. rm # Remove Files And Directories
    5. ln # Create Links，软链接”和“硬链接”的区别：硬链接指向磁盘区块，软链接指向绝对路径。

    hard links的缺点：

    1. cannot span physical devices.
    2. cannot reference directories, only files.

    5 Working With Commands(使用命令)

    1. type – Indicate how a command name is interpreted

    2. which – Display An Executable’s Location

    3. help – Get help for shell builtins

       help cd
 cd: cd [-L|[-P [-e]] [-@]] [dir]
 Change the shell working directory.

      理解注释：[]是可选，|是互斥。

    4. -help – Display Usage Information

    5. man – Display a command’s manual page

    6. info – Display a command’s info entry

      man .info .–help 的用法和区别：help最简单，info最详细，man在两者之间。

    7. apropos – Display a list of appropriate commands

    8. whatis – Display a very brief description of a command

    9. alias – Create an alias for a command

      使用：

      #起别名前先检查是否存在，用type：
tsc@tsc:~$ type test
test is a shell builtin

alias name='string' # name后不能有空格
tsc@tsc:~$ alias foo='cd /usr; ls; cd -'
tsc@tsc:~$ foo

      终端关闭后作用就消失了。

    10. unalias --去除别名

    6 – Redirection(重定向)

    1. cat - Concatenate files

      # cat file1 # 输出文件到屏幕，没有分页
cat > file.txt # cat没有参数时接受stdin*
this is test.
# ctrl+d 结束*
# < 接受文件输入*
tsc@tsc:~$ cat < lazy_dog.txt

    2. sort - Sort lines of text

    3. uniq - Report or omit repeated lines

      # -d 显示重复的
tsc@tsc:~$ ls /bin /usr/bin | sort | uniq -d | less

    4. grep - Print lines matching a pattern

      #“global regular expression print”,find功能。
tsc@tsc:~$ ls /bin /usr/bin | sort | uniq | grep zip

    5. wc - Print newline, word, and byte counts for each file

      #联合使用看条目个数：
tsc@tsc:~$ ls /bin /usr/bin | sort | uniq | wc -l

    6. head - Output the first part of a file

    7. tail - Output the last part of a file

    8. tee - Read from standard input and write to standard output and files

      这个名字很有意思，tee有三通管的意思，配合pipe使用，它的作用是从stdin读入，复制到stdout和文件。

      # 一方面输出到ls.txt，一方面传给grep
tsc@tsc:~$ ls /usr/bin/ | tee ls.txt | grep zip

    I/O redirection 的作用

    I/O redirection allows us to change where output goes and where input comes from.

    >重定向

    tsc@tsc:~$ ls -l /usr/bin/ > ls-output.txt
tsc@tsc:~$ > ls-output2.txt  # 创建一个空文件
# 要注意重复>时，原来的文件会被清空。

    >> 追加

    tsc@tsc:~$ ls -l /usr/bin >> ls-output2.txt
#文件不存在会新建。

    error 输出

    tsc@tsc:~$ ls -l /bin/usr 2> ls-error.txt
# 我的问题：在不知道有没有error的情况下，>和2>要如何同时执行？

    都输出到一个文件(有两种方法)

    # 1.老版本
# 顺序很重要
ls -l /bin/usr > ls-output.txt 2>&
# 2.新，用&>
ls -l /bin/usr &> ls-output.txt
ls -l /bin/usr &>> ls-output.txt # 追加

    Pipelines

    ls -l /usr/bin | less
#千万不要把>用成|，不然有些后果很严重。

    filters

    tsc@tsc:~$ ls /bin /usr/bin | sort | less

    7 符号变量

    这节讲expansion， 就是*、~之类的，本质就是变量。

    1. echo – Display a line of text

      It prints out its text arguments on standard output

      tsc@tsc:~$ echo this is a test
this is a test

# Tilde Expansion
tsc@tsc:~/playground$ echo ~
/home/tsc

#Arithmetic Expansion
#形式：$((expression))
tsc@tsc:~/playground$ echo $((2+2))
4

    brace expansion

    括号中间不能有空格。

    用途：批量创建有顺序的文件。

    Parameter Expansion

    Command Substitution

    command的结果也可以作为expansion

    echo $(ls)

    双引号：Double Quotes

    “$”, “” (backslash), and “`” (backquote) 失效，但是parameter expansion, arithmetic expansion, and command substitution 仍有效。

    注意区别：

    echo $(cal)
echo "$(cal)"
# 空格、tab、换行符都被用来分割，双引号则抑制。所以前一个命令不会换行，后一个会。

    单引号：Single Quotes

    抑制所有expansions

    escape character

    和双引号一起使用，抑制部分符号

    8 Advanced Keyboard Tricks(高级键盘技巧)

    这节讲键盘技巧，提高效率。主要是command line和history的技巧。command line的：移动，删除。history的上下一个命令。

    1. clear – Clear the screen
    2. history – Display the contents of the history list

    9 Permissions(权限)

    思考：多用户为什么存在？想想计算中心。

    多用户存在要解决的问题：

    1. 一个用户的错误操作不能使计算机crash
    2. 一个用户不能影响其他用户

    几个相关文件夹

    /etc/passwd
User accounts .
/etc/group
groups
/etc/shadow
user's password

    rwx Owner Group World

    1. id – Display user identity

      id
uid=1000(tsc) gid=1000(tsc) groups=1000(tsc),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),113(lpadmin),128(sambashare)
# root
# id
uid=0(root) gid=0(root) groups=0(root)

    2. chmod – Change File Mode

      chmod 600 foo.txt

    3. umask – Set Default Permissions

    4. su – Run A Shell With Substitute User And Group IDs

      默认是superuser

      su -
exit

    5. sudo – Execute A Command As Another User

      纠正自己的认识，su,sudo是改变用户的，不一定是super，默认才是。

    6. chown – Change File Owner And Group

    7. chgrp – Change Group Ownership

    8. passwd - change user password

    10 Processes(进程)

    Processes are how Linux organizes the different programs waiting for their turn at the CPU.

    1. ps - report a snapshot of the current processes.

    2. top - display Linux processes

    3. & - Putting A Process In The Background

    4. jobs - list the jobs that have been launched from our terminal.

    5. fg - Returning A Process To The Foreground

      为什么要回到前台来？后台的程序不受terminal的控制。

      Ctrl-z - Stopping (Pausing) A Process，注意和ctrl-c的区别，c是结束。

    6. bg - resume the program’s execution in the background

    7. kill - “kill” processes

    8. killall - kill processes by name

    9. halt

    10. poweroff

    11. reboot

    12. shutdown

    Part two – 配置与环境变量

    11 Environment(环境)

    什么是environment？

    configuration的作用：store program settings

    1. printenv - print all or part of environment

      # 所有environment
tsc@tsc:~$ printenv | less
# 某一个environment
tsc@tsc:~$ printenv USER
tsc@tsc:~$ echo $HOME

    2. printenv 显示的一些常见变量：

      SHELL
PATH   # 所有的，最新的

    3. set #will show both the shell and environment variables

      printenv和set的区别：printenv只显示environment variables，set显示shell和environment variables.

      追加

      PATH=$PATH:$HOME/bin

    4. export # tells the shell to make the contents of PATH available to child processes of this shell.

    序

    Login Shell Sessions ：

    /etc/profile     # global
~/.bash_profile
~/.bash_login    # 如果上面那个不存在,读这个
~/.profile       # 如果上面那个不存在,读这个
# .profile文件中有PATH，并且将$HOME/bin添加上了，所以启动系统后$HOME/bin中的命令是直接可以用的。$HOME是用户目录。

    Non-Login Shell Sessions ：

    /etc/bash.bashrc # global
~/.bashrc        # user's

    Text Editors

    有两种：

    1.graphical ：gedit

    2.text based ：nano, vi, emacs

    nano

    ctrl-x : exit
ctrl-o : save, write out
#      : comments

    使.bashrc生效

    首先要知道原理，启动流程，在session一开始才会read .bashrc，所以需要重启terminal才会生效。当然，可以强行重读.bashrc，用source命令：

    source .bashrc

    12 Gentle Introduction To vi(vi 简介)

    1. vi 操作

      :q
:q!   *# 强制退出
i     *# insert
esc   *# to command mode
:w    *# save ,有:的命令叫ex command

# move
h, j, k, l
ctrl-f/b
numberG
gg # 第一个字符
G last line of the file
0 (zero) 行首
^ To the first non-whitespace character on the current line.
$ end of current line
w beginning of next word or punctuation
W ignoring punctuation
b beginning of previous word or punctuation
B ignoring punctuation

# edit
u    # undo last change
i    # insert

# append
a    # append, i是前插
A    # 直接到最后append

# opening a line
o    # 新建一行在下面
O    # 新建一行在上面

# delete
x    # current character
3x
dd   # current line,d有cut的作用
dw   #
dW   # ignoring punctuation
d$   # current cursor to end
d0   # current cursor to beginning
dG   # current cursor to end of file
d20G # current cursor to 20 line，不是要删除20行
5dd  # 5行

# Cutting, Copying, And Pasting
p    # 小写粘贴在后一行（dd），普通在光标前
P    # 大写粘贴在前一行（dd），普通在光标后
p    # paste after cursor
P    # upper case, paste before cursor

# copy
yy   # copy current line
5yy  # copy 5 line
yW   # ignoring punctuation
yw   #
y$   # current cursor to end of line
y0   # current cursor to beginning of line
y^   # current cursor to first non-whitespace char
yG   # current cursor to last line of file
y20G # current cursor to 20th line

# redo,undo
u  			# undo
ctrl+r 	# redo
J    		# join line

# search, replace
fa   		# 行内搜索a，按;继续搜索
/    		# 文件内搜索，n继续
:%s/line/Line/g    	# 替换
:%s/line/Line/gc   	# 有提醒的替换，%代表对所有内容进行操作
:1,2s/line/Line/gc 	# 对1-2行进行操作
Ctrl-e, Ctrl-y 			# Scroll down and scroll up

    The leading tilde characters (”~”) indicate that no text exists on that line.

    modal editor

    command mode

    Switching case of characters 大小写转换

    You can change the case of text:

    Toggle case “HellO” to “hELLo” with g~ then a movement.

    Uppercase “HellO” to “HELLO” with gU then a movement.

    Lowercase “HellO” to “hello” with gu then a movement.

    Alternatively, you can visually select text then press ~to toggle case, or U to convert to uppercase, or u to convert to lowercase.

    常规操作

    # 到行尾

    $ 反：0

    A 反：I

    Word movement: w, e, b

    13 Customizing The Prompt(自定义提示)

    - PS1-prompt string one

    就是这个：

    tsc@tsc:~$

    更改它：

    tsc@tsc:~$ PS1="<u@h w>$ "
<tsc@tsc ~>$ 
u   # username of the current user.
h   # Hostname of the local machine minus the trailing domain name.
w   # Name of the current working directory.
$   # This displays a “$” character unless we have superuser privileges. In that case, it displays a “#” instead.

    改颜色：

    通过escape code 实现，escape code 的开头是八进制的033 ，例子：

    33 [0;30m
# 33 是开头
# 0   是optional character attribute，0代表text color是normal，1是bold
# 30m 是instruction
tsc@tsc:~$ PS1="[33[0;31m]<u@h w>$[33[0m] "
33[0m   *# 代表结束修改

    Part 3 – Common Tasks And Essential Tools(常见任务和基本工具)

    要知道package是什么，如何install, remove, update

    14 – Package Management(包管理)

    linux的哪个发行版才是最好的？考虑的因素不是界面，而是：

    1. packaging system
    2. vitality of the distribution’s support community

    packaging 的两大阵营：

    • Debian “.deb” camp
    • Red Hat “.rpm” camp
    Packaging System     Distributions (Partial Listing)
Debian Style (.deb)  Debian, Ubuntu, Linux Mint, Raspbian
Red Hat Style (.rpm) Fedora, CentOS, Red Hat Enterprise Linux, OpenSUSE

    - package files

    - shared libraries

    软件都是有依赖的，被依赖的就放在这里

    dependency

    - package tool

    分为high, low-level两种，

    high:metadata search, dependency

    low-level: installing, removing

    Red Hat系列使用同一low-lvel program(rpm), high-level则不同，yum使用者：Fedora, Red Hat Enter, CentOS.

    Distributions Low-Level Tools High-Level Tools

    Debian-Style dpkg apt-get, aptitude

    Fedora, Red Hat, Enterprise Linux, CentOS rpm yum

    查找和ackage的方法

    - What is the difference between apt-get update and upgrade?

    15 Storage Media(存储介质)

    什么是mounting?

    attaching the device to the file system tree.

    1. mount – Mount a file system

    没有参数时，显示已经mounted的文件系统。

    如何看？device on mount_point type file_system_type (options).

    free - Display amount of free and used memory in the system

    partition number 是什么？

    Unable to enumerate USB device under virtualbox

    usb3.0插的3.0的口上在vm中读不出来，改插在2.0的口上就可以，真是。。。

    磁盘、分区及Linux文件系统 [Disk, Partition, Linux File System]

    inode的作用：实现文件存储的关键。

    1. tail的妙用
    # ubuntu
tail -f /var/log/syslog

    实时观察系统在做什么。

    partition layout 是什么？

    IDE、SATA、SCSI、SAS、FC、SSD硬盘类型介绍

    1. fsck - check and repair a Linux filesystem

    16 Networking(网络)

    IP Addresses, Host Names, and Domain Names

    明白host name与domain name的区别。

    1. ping, ping6 - send ICMP ECHO_REQUEST to network hosts
    2. traceroute - print the route packets trace to network host
    3. ip - show / manipulate routing, devices, policy routing and tunnels

    DHCP (Dynamic Host Configuration Protocol)

    1. netstat - Print network connections, routing tables, interface statistics, masquerade connections, and multicast memberships
    2. ftp — Internet file transfer program

    ftp是明文传输。

    1. Wget - The non-interactive network downloader.
    2. ssh

    rlogin and telnet 和ftp有一样的缺陷。

    ssh解决了两大问题：First, it authenticates that the remote host is who it says it is (thus preventing so-called “man in the

    middle” attacks), and second, it encrypts all of the communications between the local and

    remote hosts.

    ssh root@ip -p 端口号

    windows下的ssh软件：PuTTY

    17 Searching For Files(文件搜索)

    找文件。

    1. locate - find files by name

      locate查找的数据库是如何更新的？由updatedb 程序更新，可以手动更新。

      locate vs find: usage, pros and cons of each other

    2. find - search for files in a directory hierarchy

      $ find ~ -type f | wc
# 文件名有jpg，大小大于1M
$ find ~ -type f -name "*.jpg" -size +1M | wc -l

#test
$ find ~ ( -type f -not -perm 0600 ) -or ( -type d -not -perm 0700 )

# 顺序很重要。
# action：把查找的结果作为命令的输入参数

$ find ~ -type f -name 'foo*' -exec ls -l '{}' ';'
$ find ~ -type f -name 'foo*' -exec ls -l '{}' +
$ find ~ -type f -name 'foo*' -print | xargs ls -l
# {} is a symbolic representation of the current pathname
# +：the system only has to execute the ls command once

#文件名中空格的处理
$ find ~ -type f -name '*.jpg' -print0 | xargs --null ls -l

    3. touch - change file timestamps

      文件不存在时会创建。

    4. stat - display file or file system status

      which is a kind of souped-up version of ls.

    18 Archiving And Backup(存档和备份)

    管理大量的文件-压缩。

    本节讲3个内容：

    compression(压缩)

    archiving(归档)

    synchronization(同步)

    1. gzip, gunzip, zcat - compress or expand files

      gzip压缩，gunzip解压。

      gzip会替换原来的文件。

    2. zcat - equivalent to gunzip with the -c option

    3. zless

    4. bzip2, bunzip2 - a block-sorting file compressor

    5. linux压缩和打包是两个要领，分别对应zip和tar，window下面是不是没有区分？

    6. tar -tape archive

      .tar or .tgz, which indicate a “plain” tar archive and a gzipped archive, respectively.

      # c create
$ tar cf playground.tar playground

# t list
$ tar tf playground.tar

# x extract
$ tar xf ../playground.tar
# r append

# extract a single file
$ tar xf archive.tar pathname

      注意区分mode与option，c是mode，f是option。mode要先写。

    7. incremental backups - 增量式备份

    8. linux shell 重定向 减号-的作用

      studout或者stdin就可以用减号（-）来替代

    9. 不解压缩直接查看.gz和.bz2命令

      使用zcat可以查看*.gz文件内容，使用bzcat可以直接查看*.bz2文件.

    10. 用ssh从远程服务器复制文件到本地

      ssh root@xxx.xxx.xx.xx -p 端口号 'tar cf - filename' | tar xf -
root@xxx.xxx.xx.xx's password:

      先tar，传回来再导出。

    11. zip - 既压缩也归档

    12. zip, unzip的作用是交换windows文件，linux用tar, gzip

    13. rsync - 备份与同步

      rsync options source destination
$ rsync -av playground foo

    19 – Regular Expressions(正则表达式)

    后面几章都是关于文字处理的。先讲regular expression.

    1. metacharacters & literal characters

      metacharacters是^ $ . [ ] { } - ? * + ( ) | ，其余就是literal characters。

    2. The Any Character

      就是点号，the dot or period character

    3. anchors

      The caret (^) (只匹配行首出来的)and dollar sign ($) （只匹配行尾出现的）

      $ grep -h '^zip' dirlist*.txt
$ grep -h 'zip$' dirlist*.txt
$ grep -h '^zip$' dirlist*.txt

    4. 点号不是任意长度吗？加上^$就代表一个？

      $ grep -h '.zip' dirlist*.txt
$ grep -i '^..j.r$' /usr/share/dict/words

    5. Bracket Expressions And Character Classes

      [] 用来只匹配一个字符。

      $ grep -h '[bg]zip' dirlist*.txt
^ : negation,只在第一个位置时有效
$ grep -h '[^bg]zip' dirlist*.txt # 注意出现的位置,表示取反
: rang$ grep -h '^[A-Za-z0-9]' dirlist*.txt
# 要匹配-（短横线），就把它放到第一位
$ grep -h '[A-Z]' dirlist*.txt
$ grep -h '[-AZ]' dirlist*.txt

    6. POSIX Character Classes

      出现的原因：posix和ASCII不一样。

    7. alternation

      []是单个，它(|)是string

      $ echo "AAA" | grep -E 'AAA|BBB|CCC'
$ grep -Eh '^(bz|gz|zip)' dirlist*.txt

    8. Quantifiers

      匹配的个数

      # ? - Match An Element Zero Or One Time ,一个字符出现的次数，和word里面的?不同，word里面代表任意一个字符，这里的?不能单独使用，要跟在一个字符后面。
$ echo "(555) 123-4567" | grep -E '^(?[0-9][0-9][0-9])? [0-9][0-9][0-9]-[0-9][0-9][0-9][0-9]$'

# * - Match An Element Zero Or More Times
$ echo "This works." | grep -E '[[:upper:]][[:upper:][:lower:] ]*.'
# 和?一样，前面要有字符。

# + - Match An Element One Or More Times 至少出现一次。
$ echo "This that" | grep -E '^([[:alpha:]]+ ?)+$'

# { } - Match An Element A Specific Number Of Times
$ echo "(555) 123-4567" | grep -E '^(?[0-9]{3})? [0-9]{3}-[0-9]{4}$'

    9. find使用reg

      $ find . -regex '.*[^-_./0-9a-zA-Z].*'
# 反 0-无穷个字符

    10. locate使用reg

      $ locate --regex 'bin/(bz|gz|zip)'

    11. less和vi中也可以使用（注意它们的区别，在vi中reg是basic）

      # less
/^([0-9]{3}) [0-9]{3}-[0-9]{4}

# vi
/([0-9]{3}) [0-9]{3}-[0-9]{4}

    20 Text Processing(文本处理)

    真是一切皆文件。

    1. cat的一些option

      $ cat -A foo.txt # 显示所有符号，包括控制符
$ cat -ns foo.txt # n显示行号，s抑制多余的空行

    2. sort

      $ sort > foo.txt
c
b
a

# 多个文件
$ sort file1.txt file2.txt file3.txt > final_sorted_list.txt

    3. du - estimate file space usage

      $ du -s /usr/share/* | head # 显示前10个
$ du -s /usr/share/* | sort -nr | head # 大到小排序后显示前10个

#按指定列排序(k)：
$ ls -l /usr/bin | sort -nr -k 5 | head

#多个key排序：
$ sort --key=1,1 --key=2n distros.txt

# 一个field内多个排序：
$ sort -k 3.7nbr -k 3.1nbr -k 3.4nbr distros.txt

#指定分割符：
$ sort -t ':' -k 7 /etc/passwd | head

    4. uniq

      $ sort foo.txt | uniq

    5. cut

      # 取第3列
$ cut -f 3 distros.txt

#每个field的长度可能不同，如果要取所有行中时间中的年，就不可能用字符位置去表示。而先把field取出来，就规整了。
$ cut -f 3 distros.txt | cut -c 7-10

    6. expand - 把tab换为等量空格

      $ expand distros.txt | cut -c 23-

    7. 改cut的默认分割符，用d option

      $ cut -d ':' -f 1 /etc/passwd | head

    8. paste

      adds one or more columns of text to a file

      $ sort -k 3.7nbr -k 3.1nbr -k 3.4nbr distros.txt > distros-by-date.txt
$ cut -f 1,2 distros-by-date.txt > distros-versions.txt
$ cut -f 3 distros-by-date.txt > distros-dates.txt
$ paste distros-dates.txt distros-versions.txt

    9. join

      It joins data from multiple files based on a shared key field.

      $ join distros-key-names.txt distros-key-vernums.txt | head

    10. comm

      $ comm file1.txt file2.txt
# -n 抑制列
$ comm -12 file1.txt file2.txt

    11. diff

      $ diff file1.txt file2.txt

# context format 看两个各自都有什么，没有什么
$ diff -c file1.txt file2.txt

# unified format 看从旧到新的变化
$ diff -u file1.txt file2.txt

    12. patch 用来更新文件，比如代码。

      apply changes to text files。

      $ diff -Naur file1.txt file2.txt > patchfile.txt

$ patch < patchfile.txt

    13. tr 转换

      $ echo "lowercase letters" | tr a-z A-Z
LOWERCASE LETTERS
#　多对一的转换
$ echo "lowercase letters" | tr [:lower:] A
# squeeze
$ echo "aaabbbccc" | tr -s ab
abccc

    14. sed：stream editor

    search-and-replace

    $ echo "front" | sed 's/front/back/'

# 谁跟在command后面就是delimiter
$ echo "front" | sed 's_front_back_'

# 指定要处理的行数
$ echo "front" | sed '1s/front/back/'

# p：打印出来
# -n：  not to print every line by default

$ sed -n '1,5p' distros.txt
$ sed -n '/SUSE/p' distros.txt
$ sed -n '/SUSE/!p' distros.txt

# 一般出输出到屏幕，用i原地
$ sed -i 's/lazy/laxy/; s/jumped/jimped/' foo.txt
​```

    1. reg的back references

      $ sed 's/([0-9]{2})/([0-9]{2})/([0-9]{4})$/3-1-2/' distros.txt

    2. 全部替换

      $ echo "aaabbbccc" | sed 's/b/B/'
$ echo "aaabbbccc" | sed 's/b/B/g'

    3. sed用script

    4. aspell 拼写检查

      $ aspell check foo.txt

# -H (HTML) checking-mode option
$ aspell -H check foo.txt

      改完了会产生一个bak文件，存在原来的文本。

    21 Formatting Output(格式化输出)

    讲文本输出格式。

    1. nl 显示行号

      $ nl distros.txt | head

# 和cat -n 一样
$ sort -k 1,1 -k 2n distros.txt | sed -f distros-nl.sed | nl

    2. fold – Wrap Each Line To A Specified Length

      $ echo "The quick brown fox jumped over the lazy dog." | fold -w 12

# 不打断单词
$ echo "The quick brown fox jumped over the lazy dog." | fold -w 12 -s

    3. fmt – A Simple Text Formatter

      it fills and joins lines in text while preserving blank lines and indentation.

      $ fmt -w 50 fmt-info.txt | head
$ fmt -cw 50 fmt-info.txt
# 一行如果不足50个字符，会把第二行的补过来
# 只对'# '开头的行操作
$ fmt -w 50 -p '# ' fmt-code.txt

    4. pr – Format Text For Printing

      used to paginate text.

      # l:page length
# w:width
$ pr -l 15 -w 65 distros.txt

#首尾会有空行。

    5. printf – Format And Print Data

      #使用：printf “format” arguments
$ printf "I formatted the string: %s
" foo
$ printf "%d, %f, %o, %s, %x, %X
" 380 380 380 380 380 380

#Multiple optional components ：
%[flags][width][.precision]conversion_specification

    6. Document Formatting Systems

      tex后来取代了troff.

    7. groff

      $ zcat /usr/share/man/man1/ls.1.gz | head
$ man ls | head
$ zcat /usr/share/man/man1/ls.1.gz | groff -mandoc -T ascii | head

# 存为postscript到桌面
$ zcat /usr/share/man/man1/ls.1.gz | groff -mandoc > ~/Desktop/foo.ps

# ps转pdf
$ ps2pdf ~/Desktop/foo.ps ~/Desktop/ls.pdf

    8. tbl

    22 Printing(打印)

    介绍了ps的由来。

    CUPS (Common Unix Printing System) ：provides print drivers and print-job management

    Ghostscript： a PostScript interpreter, acts as a RIP.

    1. pr – Convert Text Files For Printing

      pr is used to adjust text to fit on a specific page size, with optional page headers and margins.

      # 3列
$ ls /usr/bin | pr -3 -w 65 | head

    CUPS 有两种printing，lpr, lp.

    1. lpr – Print Files (Berkeley Style)

      $ ls /usr/bin | pr -3 | lpr

    2. lpr: Error - no default destination available.

      # 查看printer
$ lpstat -a
lpstat: No destinations added.

    3. lp – Print Files (System V Style)

    4. a2ps

      “Anything to PostScript.”
$ ls /usr/bin | pr -3 -t | a2ps -o ~/Desktop/ls.ps -L 66 -R

    5. lpstat – Display Print System Status

      # 查询printer状态
$ lpstat -a
$ lpstat -a

    6. lpq – Display Printer Queue Status

      $ lpq
PDF is ready
no entries

    7. lprm / cancel – Cancel Print Jobs

    23 – Compiling Programs(程序编译)

    1. compile

      linker，解决共享问题，用共享库。

      $ which gcc
/usr/bin/gcc

    2. 用ftp下载source code

      $ mkdir src
$ cd src

$ ftp ftp.gnu.org
Name (ftp.gnu.org:me): anonymous
ftp> cd gnu/diction
ftp> ls
ftp> get diction-1.11.tar.gz
ftp> bye
$ tar xzf diction-1.11.tar.gz

# 先查看是不是在一个文件夹里，以免解压散开
$ tar tzvf diction-1.11.tar.gz | less

      共享的头文件在/usr/include ，The header files in this directory were installed when we installed the compiler.

    3. Building The Program

      一般需要两步。

      # 由于script不在默认的目录，需要./告诉shell它在当前目录
$ ./configure

config.status: creating Makefile
config.status: creating diction.1
config.status: creating diction.texi
config.status: creating diction.spec
config.status: creating style.1
config.status: creating test/rundiction
config.status: creating config.h

# Makefile is a configuration file that instructs the make program exactly how to build the program. Without it, make will refuse to run.
#make只complie需要complie的文件，省时间。
$ make	&& make install
#Installing The Program

    Part 4 – Writing Shell Scripts(编写shell脚本)

    24 – Writing Your First Script(开始你的第一个脚本)

    1. script开头的#!

      shebang，指明interpreter，每个script开头都应该加这行。

    2. 让script可以执行

      $ chmod 755 hello_world

      owner的权限是x就可以了。755所有人可以执行，700只有owner可以执行。必须是可读的。

    3. 执行

      $ ./hello_world

      必须要加上./ ,因为文件位置的问题。自动识别的命令的目录都写在了PATH中，可以查看它：

      $ echo $PATH

    4. 把某个路径添加到PATH

      在.bashrc （它在~中）中添加：

      # 把~/bin添加在PATH的前面
export PATH=~/bin:"$PATH"

# 在当前terminal中生效
$ ..bashrc

# 或者
$ source .bashrc

    5. script放哪？

       ~/bin ： 自己用
 /usr/local/bin ： 同一个系统多人用
 /usr/local/sbin： 系统管理员用
 /usr/local：   locally supplied software，

    6. line-continuations

      就是

    7. vi中对script的配置

      :syntax on
:set hlsearch
:set tabstop=4
:set autoindent

永久：
写在~/.vimrc，没有就创建

    25 – Starting A Project(开始)

    shell是动态语言

    uppercase letters to designate constants and lower case

    letters for true variables.

    $ vim ~/bin/sys_info_page
$ chmod 755 ~/bin/sys_info_page
$ sys_info_page
$ sys_info_page > sys_info_page.html
$ firefox sys_info_page.html

    变量(Variables) 与 常量（Constants）

    用于指定常量的大写字母和用于真实变量的小写字母（uppercase letters to designate constants and lower case letters for true variables.）

    Note that in an assignment, there must be no spaces between the variable name, the equals sign, and the value.

    a=z                  # Assign the string "z" to variable a.
b="a string"         # Embedded spaces must be within quotes.
c="a string and $b"  # Other expansions such as variables can be 

# expanded into the assignment.
d="$(ls -l foo.txt)" # Results of a command.
e=$((5 * 7))         # Arithmetic expansion.
f="		a string
"   # Escape sequences such as tabs and newlines.

    大括号的作用

    $ filename="myfile"
$ touch "$filename"
$ mv "$filename" "$filename1"
mv: cannot move 'myfile' to '': No such file or directory

$ mv "$filename" "${filename}1"

    here document

    command << token
text
token

# shell example
cat << _EOF_
<HTML>
    <HEAD>
        <TITLE>$TITLE</TITLE>
    </HEAD>
</HTML>
_EOF_

# terminal example

$ cat << _EOF_

> $foo
> "$foo"
> '$foo'
> $foo
> _EOF_

    26 Top-Down Design(自上而下的设计)

    讲程序设计的思想。

    shell functions

    两种形式：

    function name {
  commands
  return
}

and the simpler (and generally preferred) form:

name () {
  commands
  return
}

    in order for function calls to be recognized as shell functions and not interpreted as the names of external programs, shell function definitions must appear in the script before they are called.

    local variables

    要加local

    funct_1 () {
    local foo # variable foo local to funct_1
    foo=1
    echo "funct_1: foo = $foo"
}

    27 – Flow Control: Branching With if(流程控制：if分支)

    shell的if语句挺复杂的。

    if commands; then
    commands
[elif commands; then
    commands...]
[else
    commands]
fi

x=5

if [ "$x" -eq 5 ]; then
    echo "x equals 5."
else
    echo "x does not equal 5."
fi

    exit status

    程序结果后返回给系统的。查询：

    $ ls -d /usr/bin
$ echo $?

    true - do nothing, successfully

    false - do nothing, unsuccessfully

    test

    语法：

    test expression
and the more popular:
[ expression ]

    expression是true时返回0，否则返回1

    test和[ 本质上是一样的。

    使用：

    #!/bin/bash
# test-file: Evaluate the status of a file

FILE=~/.bashrc

if [ -e "$FILE" ]; then
    if [ -f "$FILE" ]; then
        echo "$FILE is a regular file."
    fi
    
    if [ -d "$FILE" ]; then
        echo "$FILE is a directory."
    fi
    
    if [ -r "$FILE" ]; then
        echo "$FILE is readable."
    fi
    
    if [ -w "$FILE" ]; then
        echo "$FILE is writable."
    fi
    
    if [ -x "$FILE" ]; then
        echo "$FILE is executable/searchable."
    fi
else
    echo "$FILE does not exist"
    exit 1
fi

exit  # ?

    When a script “runs off the end” (reaches end of file), it terminates with an exit status of the last command executed.

    String Expressions

    #!/bin/bash
# test-string: evaluate the value of a string

ANSWER=maybe

if [ -z "$ANSWER" ]; then
    echo "There is no answer." >&2
    exit 1
fi

if [ "$ANSWER" = "yes" ]; then
    echo "The answer is YES."
elif [ "$ANSWER" = "no" ]; then
    echo "The answer is NO."
elif [ "$ANSWER" = "maybe" ]; then
    echo "The answer is MAYBE."
else
    echo "The answer is UNKNOWN."

    Integer Expressions

    test的选项真多！！！

    test用regex

    [[]]

    # 检验是不是数
if [[ "$INT" =~ ^-?[0-9]+$ ]]; then

    (( )) - Designed For Integers

    $ if ((1)); then echo "It is true."; fi

It is true.

if ((INT == 0)); 

if ((INT < 0)); 

if (( ((INT % 2)) == 0));

    Combining Expressions

    Operation   test   [[ ]] and (( ))
AND         -a           &&
OR          -o           ||
NOT         !            !

    例子：

    # [[]]
if [[ "$INT" -ge "$MIN_VAL" && "$INT" -le "$MAX_VAL" ]];

# test
if [ "$INT" -ge "$MIN_VAL" -a "$INT" -le "$MAX_VAL" ];

    Control Operators: Another Way To Branch

    The && (AND) and || (OR)

    $ mkdir temp && cd temp
$ [[ -d temp ]] || mkdir temp

    []和[[]]的区别

    [[]]和[]一样，不过有两个新特性，：

    string1 =~ regex

    == operator

    [[]]和表达式之间要有空格

    [[ "$count" -gt 5 ]]
[[ "$count" -gt 5]] # 会报错，执行起来会很可怕

    28 Reading Keyboard Input(读取键盘输入)

    read – Read Values From Standard Input

    read a single line of standard input.

    read [-options] [variable…]

    # -n option,suppresses the trailing newline on output
echo -n "Please enter an integer -> "

read int
read var1 var2 var3 var4 var5 # 多个

# -p prompt
read -p "Enter one or more values > "

# -t seconds
# -s Silent mode. 
if read -t 10 -sp "Enter secret passphrase > " secret_pass;

    IFS

    Internal Field Separator

    file_info=$(grep "^$user_name:" $FILE)
# 写在一行，IFS只改变跟在后面的 command
IFS=":" read user pw uid gid name home shell <<< "$file_info"

    here string

    The <<< operator indicates a here string.

    You Can’t Pipe read

    就像函数与子函数，凡是这一类都不能pip。

    Validating Input

    Menus

    29 – Flow Control: Looping With while / until(流程控制：while/until)

    有3各loop

    while

    语法：

    while commands; do commands; done

#!/bin/bash

# while-count: display a series of numbers
count=1

while [[ "$count" -le 5 ]]; do
    echo "$count"
    count=$((count + 1))
done
echo "Finished."

    Breaking Out Of A Loop：break、continue、until

    和while相反

    count=1
until [[ "$count" -gt 5 ]]; do
    echo "$count
    count=$((count + 1))
done
echo "Finished.

    read file with loop

    #!/bin/bash
# while-read

while read distro version release; do
    printf "distro: %s	version: %s	released: %s
" 
        "$distro" 
        "$version" 
        "$release"
done < distros.txt

    30 – Troubleshooting

    讲错误的处理。

    引号不对称

    特定符号缺失

    意外的expansion

    是否报错取决于expansion的值。

    双引号的作用

    # number为空时会报错
number=
if [ $number = 1 ]; then

# 这样就不会了  “”=1
[ "$number" = 1 ]

    Multi-word string也应该用双引号括起来。

    所以，总是用双引号把变量括起来。

    logical error

    给出错误信息是比较好的做法

    unix文件名称什么字符都可以用，有两个例外

    / , null character(a zero byte)

    the POSIX Portable Filename Character Set

    uppercase letters A-Z, lowercase letters a-z, numerals 0-9, period (.), hyphen (-), and underscore(_).

    检查input

    要会写测试

    利用echo输出

    在更改的地方加注释，方便恢复。

    test case

    case要反映edge and corner

    debug技术

    commenting out :部分注释

    tracing :在一些关键点增加输出，查看是否执行到这里了

    可以在script的第一行加入x option:

    #!/bin/bash -x

    也可以用set设置部分tracing

    set -x # turn on
...
set +x # turn off

    输出中间过程中变量的值

    推荐《The Art of Unix Programming》

    31 – Flow Control: Branching With case(流程控制 case分支)

    case的用法

      #!/bin/bash
  # case-menu
  
  clear
  echo "
  please select:
  
1. display system information
2. display disk space
3. display home space utilization
0. quit
"
read -p "enter selection [0-3] > "

case "$REPLY" in
    0)  echo "program terminated"
        exit
        ;;
    1)  echo "hostname: $HOSTNAME"
        uptime
        ;;
    2)  df -h
        ;;
    3) if [[ "$(id -u)" -eq 0 ]]; then
            echo "home space utilization (all users)"
            du -sh /home/*
        else
            echo "home space utilization ($USER)"
            du -sh "$HOME"
        fi
        ;;
    *)  echo "invalid entry" >&2
        exit 1
        ;;
esa

    32 – Positional Parameters(位置参数)

    讲处理command的option

    positional parameter

    $0是当前命令的路径。

    注意它的含义：

    Note that $0 always contains the full pathname of the first item on the command line (i.e., the name of the program) and does not contain the name of the shell function as we might expect.

    是整个路径，不是命令的名字。

    大于9时用大括号括起来。

    参数个数：$#

    shift

    让$1下次变成2，所有参数都移动，2，所有参数都移动，#减1

    basename

    去除文件名前面的字符，只要文件名。

    positional parameter也可以用在function中

    Difference between echo -e “” and echo $“”

    e的意思就是扩展，支持转义，e和$支持的符号部分不相同。

    ∗和*和@的区别

    不加双引号时是一样的，遇到空格就拆分，加双引号时不一样，∗会将所有参数放到一个字符串中，*会将所有参数放到一个字符串中，@会将每个输入的参数分别当作参数，也就是不区分输入时的空格。

    $@经常用。

    33 – Flow Control: Looping With for(流程控制:for循环)

    讲for

    # 两种风格

for variable [in words]; do
    commands
done

# c语言的

for (( expression1; expression2; expression3 )); do
    commands
done

    例子：

    [me@linuxbox ~]$ for i in A B C D; do echo $i; done

    Create list:

    itscs-MacBook-Pro:~ itsc$ for i in {A..D}; do echo $i; done

# 文件列表 pathname expansion
itscs-MacBook-Pro:learnCommandLine itsc$ for i in dis*.txt; do echo "$i"; done

    34 – Strings And Numbers(字符与数字)

    一般情况下将变量括起来，防止被拆分

    parameter expansion是什么？

    变量是其中的一种

    大括号的作用

    $a
${a}
a="foo"
echo "${a}_file" # 和其它字符相连时防止形成不存在的变量

    处理空的和不存在的字符

    parameter为空或者不存在就用word，存在就用它自己。
${parameter:-word}

和上面基本一样，区别：要赋值。
${parameter:=word}

unset和empty就发发送word到error
${parameter:?word}

${parameter:+word}

    String operation(字符串操作符)

    ${#parameter} # 换成长度

$ foo="This string is long."
$ echo "'$foo' is ${#foo} characters long.
'This string is long.' is 20 characters long

${parameter:offset}
${parameter:offset:length}
[me@linuxbox ~]$ foo="This string is long."
[me@linuxbox ~]$ echo ${foo:5}
string is long.
[me@linuxbox ~]$ echo ${foo:5:6}
string

删除一部分
${parameter#pattern}
${parameter##pattern}
[me@linuxbox ~]$ foo=file.txt.zip
[me@linuxbox ~]$ echo ${foo#*.}
txt.zip
[me@linuxbox ~]$ echo ${foo##*.}
zip

反着删除
${parameter%pattern}
${parameter%%pattern}
[me@linuxbox ~]$ foo=file.txt.zip
[me@linuxbox ~]$ echo ${foo%.*}
file.txt
[me@linuxbox ~]$ echo ${foo%%.*}
file

替换
${parameter/pattern/string}
${parameter//pattern/string}
${parameter/#pattern/string}
${parameter/%pattern/string}

    可以用expansion来提高script的效率

    大小写转换

    可以用来做什么？比如数据库的查找，匹配的时候把输入和数据库中的都统一大小写。

    declare

    shell不能进行浮点运算

    itscs-MacBook-Pro:learnCommandLine itsc$ echo $((3.3+4.2))
-bash: 3.3+4.2: syntax error: invalid arithmetic operator (error token is ".3+4.2")

    解决：perl, awk.书里用最简单的bc

    为什么连浮点运算都不支持？真是麻烦。

    35 – Arrays(数组)

    scalar variables

    Single value

    shell的array只能一维

    [me@linuxbox ~]$ a[1]=foo
[me@linuxbox ~]$ echo ${a[1]}
foo
[me@linuxbox ~]$ declare -a a

# assign
name[subscript]=value
name=(value1 value2 ...)
[me@linuxbox ~]$ days=(Sun Mon Tue Wed Thu Fri Sat)
[me@linuxbox ~]$ days=([0]=Sun [1]=Mon [2]=Tue [3]=Wed [4]=Thu [5]=Fri [6]=Sat)

    遍历array

    [me@linuxbox ~]$ animals=("a dog" "a cat" "a fish")
[me@linuxbox ~]$ for i in ${animals[*]}; do echo $i; done
[me@linuxbox ~]$ for i in ${animals[@]}; do echo $i; done
[me@linuxbox ~]$ for i in "${animals[*]}"; do echo $i; done
[me@linuxbox ~]$ for i in "${animals[@]}"; do echo $i; done

    bash的array不一定是要连续的

    所以需要有方法知道哪些位置上有值

    [me@linuxbox ~]$ foo=([2]=a [4]=b [6]=c)

[me@linuxbox ~]$ for i in "${foo[@]}"; do echo $i; done
a
b
c

[me@linuxbox ~]$ for i in "${!foo[@]}"; do echo $i; done
2
4
6

    array的追加

    $ foo=(a b c)
$ foo[100]=e
$ echo ${foo[@]}
a b c e
$ foo+=(k l)
$ echo ${foo[@]}
a b c e k l
$ for i in "${foo[@]}"; do echo $i; done
a
b
c
e
k
l
$ for i in "${!foo[@]}"; do echo $i; done
0
1
2
100
101
102

    subscript不是连续的

    associative arrays

    下标可以是字符

    36 – Exotica(特殊)

    讲一些不常用的，在特定场景下使用的

    Group Commands And Subshells

    Group command:
{ command1; command2; [command3; ...] }
Subshell:
(command1; command2; [command3;...])

    它们是做什么的？

    manage redirection

    { ls -l; echo "Listing of foo.txt"; cat foo.txt; } > output.txt
(ls -l; echo "Listing of foo.txt"; cat foo.txt) > output.txt

    结合pip

    { ls -l; echo "Listing of foo.txt"; cat foo.txt; } | lpr

    注意大括号的使用

    due to the way bash implements

    group commands, the braces must be separated from the commands by a space and the

    last command must be terminated with either a semicolon or a newline prior to the closing brace.

    group和subshell的区别

    subshell和它的名字一样，返回时enviroment会丢失，所以一般情况下用group.

    echo "foo" | read
echo $REPLY # 这就是subshell的例子，reply是空的

    commands in pipelines are always executed in subshells

    process substitution

    用来解决subshell的问题

    read <<(echo "foo")
echo $REPLY

    asynchronous execution

    什么是异步？

    什么是阻塞，非阻塞，同步，异步？

    举个打电话的例子：

    阻塞/同步：打一个电话一直到有人接为止

    非阻塞：打一个电话没人接，每隔10分钟再打一次，知道有人接为止

    异步：打一个电话没人接，转到语音邮箱留言（注册），然后等待对方回电（call back)

    看起来异步是最高效，充分利用资源，可以想像整个系统能支持大规模并发。但问题是调试很麻烦，不知道什么时候call back。

    Named pipes

    create a connection between two processes and can be

    used just like other types of files.

    named pipe是一个文件起着pipe的作用

    [me@linuxbox ~]$ mkfifo pipe1

[me@linuxbox ~]$ ls -l pipe1
prw-r--r-- 1 me me 0 2009-07-17 06:41 pipe1

# terminal 1
[me@linuxbox ~]$ ls -l > pipe1

# terminal2
[me@linuxbox ~]$ cat < pipe1

    问题

    [[:upper:]]哪一节的？

    每个文件夹下的.和…的作用？为什么必须要有它们？

    它们代表当前和前一级目录，这个大家都知道，可以为什么要有它们？设计原理是什么？

    参考：SO，只说了有，没有说什么为什么。

    shell中各种括号[]、[[]]的作用与区别？

    参考。

    需要了解的知识

    linux文件系统

    磁盘、分区及Linux文件系统 [Disk, Partition, Linux File System

    硬盘接口

    IDE、SATA、SCSI、SAS、FC、SSD硬盘类型介绍

    Understand synopsis in manpage

    可以直接在命令man man中看。

    vi color

    ENABLING VI SYNTAX COLORS

    cd ~
vi .vimrc
syntax on
colorscheme desert

    vi indent

    # 添加到vimrc中即永久：
set tabstop=4

    标准错误输出>&2输出到哪了？屏幕。

    vim color

    /usr/share/vim/vim74/colors/

    我觉得还不错的：

    koehler

    industry

    murphy

    ron

    ls如何按文件类型排序？

    ls -lX

    vi comment

    Reveal the line numbers:

    :set number

#then 
:5,$s/^/#/g     comment 
#or
:5,$s/^/#/      uncomment

    单引号、双引号区别

    echo $1
echo "$1"
echo '$1'

$ ./longest words
words
words

    双引号与无引号在这里是一样的，双引号的作用体现在字符串为空的时候，为空的时候是空字符串，可以判断，而无引号就麻烦了，比如等号，一边为空会报错，说等号是个二元操作符两边都要有值。单引号的作用就是禁止转义，全部为字符串。

    [linux中shell变量#,#,@,0,0,1,$2的含义解释](
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  • 原文地址：https://www.cnblogs.com/daozhangblog/p/12446322.html
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