Reference

• http://blog.jobbole.com/86948/ : 11个让你吃惊的 Linux 终端命令
• http://coolshell.cn/articles/8883.html : 应该知道的Linux技巧(from coolshell)
• http://coolshell.cn/articles/4990.html : 程序员技术练级攻略
• http://linuxtools-rst.readthedocs.org/zh_CN/latest/index.html : Linux工具快速教程(complete)

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Bash Shell Shortcut

• 在 bash 里，使用 Ctrl-R 而不是上下光标键来查找历史命令。
• 在 bash里，使用 Ctrl-W 来删除最后一个单词，使用 Ctrl-U 来删除一行。请man bash后查找Readline Key Bindings一节来看看bash的默认热键，比如：Alt-. 把上一次命令的最后一个参数打出来，而Alt-* 则列出你可以输入的命令。

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System Directory Structure

• /bin : All the executable binary programs (file) required during booting, repairing, files required to run into single-user-mode, and other important, basic commands 需要在[单用户模式]可用的必要命令（[可执行文件]）；面向所有用户，例如：cat, ls, cp.
• /boot : Holds important files during boot-up process, including Linux Kernel.
• /dev : Contains device files for all the hardware devices on the machine e.g., cdrom, cpu, etc
• /etc : Contains Application’s configuration files, startup, shutdown, start, stop script for every individual program.
• /home : Home directory of the users. Every time a new user is created, a directory in the name of user is created within home directory which contains other directories. For Mac, user files are stored in Users.
• /lib : The Lib directory contains kernel modules and shared library images required to boot the system and run commands in root file system.
• /media : Temporary mount directory is created for removable devices viz., media/cdrom.
• /mnt : Temporary mount directory for mounting file system.
• /opt : Optional is abbreviated as opt. Contains third party application software. Viz., Java, etc.
• /proc : A virtual and pseudo file-system which contains information about running process with a particular Process-id aka pid.
• /root : This is the home directory of root user and should never be confused with ‘/‘
• /run : This directory is the only clean solution for early-runtime-dir problem.
• /sbin : Contains binary executable programs, required by System Administrator, for Maintenance. 必要的系统二进制文件，例如： init、 ip、 mount。
• /srv : Service is abbreviated as ‘srv‘. This directory contains server specific and service related files.
• /sys : Modern Linux distributions include a /sys directory as a virtual filesystem, which stores and allows modification of the devices connected to the system.
• /tmp :System’s Temporary Directory, Accessible by users and root. Stores temporary files for user andsystem, till next boot.
• /usr : Contains executable binaries, documentation, source code, libraries for second level program.
• /var : Stands for variable. The contents of this file is expected to grow. This directory contains log, lock,spool, mail and temp files.

Some further explanation

• bin is different from lib. bin is for binary file, while lib or Library is for library (like dynamic/static linking library).

• /usr – User Programs
  Contains binaries, libraries, documentation, and source-code for second level programs.

  • /usr/bin contains binary files for user programs. If you can’t find a user binary under /bin, look under /usr/bin. For example: at, awk, cc, less, scp. 非必要可执行文件(在单用户模式中不需要)；面向所有用户。
  • /usr/sbin contains binary files for system administrators. If you can’t find a system binary under /sbin, look under /usr/sbin. For example: atd, cron, sshd, useradd, userdel. 非必要的系统二进制文件，例如：大量[网络服务]的[守护进程]。
  • /usr/lib contains libraries for /usr/bin and /usr/sbin
  • /usr/local contains users programs that you install from source. For example, when you install apache from source, it goes under /usr/local/apache2. 本地数据的第三层次， 具体到本台主机。通常而言有进一步的子目录， 例如：bin/, lib/, share/.

• /lib – System Libraries
  Contains library files that supports the binaries located under /bin and /sbin
  Library filenames are either ld* or lib.so.
  For example: ld-2.11.1.so, libncurses.so.5.7

• /etc – Configuration Files
  Contains configuration files required by all programs.
  This also contains startup and shutdown shell scripts used to start/stop individual programs.
  For example: /etc/resolv.conf, /etc/logrotate.conf

• /bin – User Binaries
  Contains binary executables.
  Common linux commands you need to use in single-user modes are located under this directory.
  Commands used by all the users of the system are located here.
  For example: ps, ls, ping, grep, cp.

• /sbin – System Binaries
  Just like /bin, /sbin also contains binary executables.
  But, the linux commands located under this directory are used typically by system aministrator, for system maintenance purpose.
  For example: iptables, reboot, fdisk, ifconfig, swapon

• /etc/ssh/

Other important directories under user directory:

• /Users/abrocod/.ssh
• /Users/abrocod/.aws

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Common Shell Command

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Simple Command Collection

• which
• whereis
• whoami
• date
• printenv
• env
• alias

alias ls='ls --color=auto'
alias grep='grep --color=auto'

sudo -i # run as root user
sudo !!
sudo -E

ls

-l ：列出长数据串，包含文件的属性与权限数据等
-a ：列出全部的文件，连同隐藏文件（开头为.的文件）一起列出来（常用）
-d ：仅列出目录本身，而不是列出目录的文件数据
-h ：将文件容量以较易读的方式（GB，kB等）列出来
-R ：连同子目录的内容一起列出（递归列出），等于该目录下的所有文件都会显示出来

du, df

check directory size and check the whole disk space utility
du -sh
du -h
df -h

grep

grep [-acinv] [--color=auto] '查找字符串' filename

-a ：将binary文件以text文件的方式查找数据
-c ：计算找到‘查找字符串’的次数
-i ：忽略大小写的区别，即把大小写视为相同
-v ：反向选择，即显示出没有‘查找字符串’内容的那一行

------- 例如：-------
取出文件/etc/man.config中包含MANPATH的行，并把找到的关键字加上颜色:
grep --color=auto 'MANPATH' /etc/man.config
把ls -l的输出中包含字母file（不区分大小写）的内容输出:
ls -l | grep -i file

• search for pattern

grep "pattern" -r *

cut

clean file:
cut -c3-73 sample_thumbid.txt > clean_tbnail.txt

find

find [PATH] [option] [action]
与时间有关的参数：
-mtime n : n为数字，意思为在n天之前的“一天内”被更改过的文件；
-mtime +n : 列出在n天之前（不含n天本身）被更改过的文件名；
-mtime -n : 列出在n天之内（含n天本身）被更改过的文件名；
-newer file : 列出比file还要新的文件名
例如：
find /root -mtime 0 # 在当前目录下查找今天之内有改动的文件

与用户或用户组名有关的参数：
-user name : 列出文件所有者为name的文件
-group name : 列出文件所属用户组为name的文件
-uid n : 列出文件所有者为用户ID为n的文件
-gid n : 列出文件所属用户组为用户组ID为n的文件
例如：
find /home/ljianhui -user ljianhui # 在目录/home/ljianhui中找出所有者为ljianhui的文件

与文件权限及名称有关的参数：
-name filename ：找出文件名为filename的文件
-size [+-]SIZE ：找出比SIZE还要大（+）或小（-）的文件
-tpye TYPE ：查找文件的类型为TYPE的文件，TYPE的值主要有：一般文件（f)、设备文件（b、c）、
目录（d）、连接文件（l）、socket（s）、FIFO管道文件（p）；
-perm mode ：查找文件权限刚好等于mode的文件，mode用数字表示，如0755；
-perm -mode ：查找文件权限必须要全部包括mode权限的文件，mode用数字表示
-perm +mode ：查找文件权限包含任一mode的权限的文件，mode用数字表示
例如：
find / -name passwd # 查找文件名为passwd的文件
find ./ -name '.o'
find ./ -name ".o" -exec rm {} ;
find . -perm 0755 # 查找当前目录中文件权限的0755的文件
find . -size +12k # 查找当前目录中大于12KB的文件，注意c表示byte

cp

-a ：将文件的特性一起复制
-p ：连同文件的属性一起复制，而非使用默认方式，与-a相似，常用于备份
-i ：若目标文件已经存在时，在覆盖时会先询问操作的进行
-r ：递归持续复制，用于目录的复制行为
-u ：目标文件与源文件有差异时才会复制

cp -a file1 file2 #连同文件的所有特性把文件file1复制成文件file2
cp file1 file2 file3 dir #把文件file1、file2、file3复制到目录dir中

mv

-f ：force强制的意思，如果目标文件已经存在，不会询问而直接覆盖
-i ：若目标文件已经存在，就会询问是否覆盖
-u ：若目标文件已经存在，且比目标文件新，才会更新

mv file1 file2 file3 dir # 把文件file1、file2、file3移动到目录dir中
mv file1 file2 # 把文件file1重命名为file2

rm

-f ：就是force的意思，忽略不存在的文件，不会出现警告消息
-i ：互动模式，在删除前会询问用户是否操作
-r ：递归删除，最常用于目录删除，它是一个非常危险的参数

rm -i file # 删除文件file，在删除之前会询问是否进行该操作
rm -fr dir # 强制删除目录dir中的所有文件

file

file filename
例如：
file ./test

tar

-c ：新建打包文件
-t ：查看打包文件的内容含有哪些文件名
-x ：解打包或解压缩的功能，可以搭配-C（大写）指定解压的目录，注意-c,-t,-x不能同时出现在同一条命令中
-j ：通过bzip2的支持进行压缩/解压缩
-z ：通过gzip的支持进行压缩/解压缩
-v ：在压缩/解压缩过程中，将正在处理的文件名显示出来
-f filename ：filename为要处理的文件
-C dir ：指定压缩/解压缩的目录dir

压缩：tar -zcvf filename.tar.gz 要被处理的文件或目录名称
查询：tar -ztvf filename.tar.gz
解压：tar -zxvf filename.tar.gz -C 欲解压缩的目录

tar -zcvf test.tar.gz *
Note: -f option must follow the filename !!!

-- if the file is just .tar, not .tar.gz or .tar.bz2, then use:
tar -xvf filename.tar -C ./dir

-- if the file is just a .zip
unzip file.zip -d destination_folder

zip

zip squash.zip file1 file2 file3
zip -r squash.zip dir1 # zip recursively, -r
unzip squash.zip

use less squash.zip to look at the content of zip file
or use 'unzip -l squash.zip', which is the same as less

ln

ln cc ccAgain :硬连接；删除一个，将仍能找到；
ln -s cc ccTo :符号链接(软链接)；删除源，另一个无法使用；（后面一个ccTo 为新建的文件）

ln -s TARGET LINK_NAME

• Find the link after softlink

ls -l `which java`
lrwxr-xr-x  1 root  wheel  74 Sep  1 15:27 /usr/bin/java -> /System/Library/Frameworks/JavaVM.framework/Versions/Current/Commands/java

chgrp, chown

chgrp [-R] dirname/filename
-R ：进行递归的持续对所有文件和子目录更改
例如：
chgrp users -R ./dir # 递归地把dir目录下中的所有文件和子目录下所有文件的用户组修改为users

groups <username> -- check which group user belongs to

-- chown
chown owner-user file
chown owner-user:owner-group file
chown owner-user:owner-group directory
chown options owner-user:owner-group file

e.g:
chown vivek demo.txt # change owner
chown vivek:vivek demo.txt # change owner and group
chown :ftp demo.txt # change only group
chown -R vivek /home/vivek # recursively change

open file in Ubuntu

You can use:
gnome-open file2open.xxx (xxx = some file extension).
With this command gnome will invoke the default app for "xxx"

----------- for example evince if you want to open pdf ------------
Or specifically:
evince file2open.pdf

Or (default for KDE):
okular file2open.pdf

process management

ps

ps [aux]
ps aux | grep 'chrome' | less

pstree

top

Top will give you a realtime view of the system and only show the number of processes which will fit on the screen.

kill

kill [signal] <PID>
e.g:
kill 6978
kill -1 6978 // kill/quit the process gently
kill -9 6978 // kill the process with brutal force

lsof

If you know what port the process is running you can type: lsof -i:<port>. For instance, lsof -i:8080, to list the process (pid) running on port 8080. Then kill the process with kill <pid>

tail

The command tail -f will display the last 10 lines of a file, and then continuously wait for new lines, and display them as they appear.

$ tail -f /var/log/messages

If you want to see more than ten lines at the outset, specify the new number (say 50 lines) like this:

$ tail -50 -f /var/log/messages

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