缩写习惯
无聊和乏味的工作是罪恶
-- Eric S. Raymond
构建于图形界面之上的操作系统，使用鼠标作为主输入设备， 是否使用缩写并不重要。比如 Windows 系统中的目录，几乎都是全称…… 点击两次鼠标进入文件夹 pf， 并不意味着点击13次才能进入文件夹 Program Files
而构建于命令行之上的操作系统，如 Linux，只要3个字母以上的单词，几乎都要缩写。 例如： cd 命令是 Change Directory 的缩写。 作为常用命令，如果使用它的全称 Change Directory，绝对是无聊和乏味的工作。
最常见的缩写，取每个单词的首字母，如
| cd | Change Directory |
| dd | Disk Dump |
| df | Disk Free |
| du | Disk Usage |
| pwd | Print Working Directory |
| ps | Processes Status |
| PS | Prompt Strings |
| su | Substitute User |
| rc | Run Command |
| Tcl | Tool Command Language |
| cups | Common Unix Printing System |
| apt | Advanced Packaging Tool |
| bg | BackGround |
| ping | Packet InterNet Grouper |
如果首字母后为“h”，通常保留
| chsh | CHange SHell |
| chmod | CHange MODe |
| chown | CHange OWNer |
| chgrp | CHange GRouP |
| bash | Bourne Again SHell |
| zsh | Z SHell |
| ksh | Korn SHell |
| ssh | Secure SHell |
递归缩写[]也属于这一类，如：
| GNU | GNU's Not Unix |
| PHP | PHP: Hypertext Preprocessor |
| RPM | RPM Package Manager |
| WINE | WINE Is Not an Emulator |
| PNG | PNG's Not GIF |
| nano | Nano's ANOther editor |
有些缩写可能有多种定义，如：
rpm RPM Package Manager RedHat Package Manager bc Basic Calculator Better Calculator
这方面 Emacs 可谓独领风骚：
Emacs Editor MACroS Emacs Makes A Computer Slow Escape Meta Alt Control Shift Emacs Makers Are Crazy Sickos Emacs Makes All Computing Simple Emacs Makefiles Annihilate C-Shells Emacs Manuals Always Cause Senility Emacs May Allow Customized Screwups Emacs Manuals Are Cryptic and Surreal Eventually Munches All Computer Storage Eight Megabytes And Constantly Swapping Elsewhere Maybe All Commands are Simple Excellent Manuals Are Clearly Suppressed Emacs May Alienate Clients and Supporters Except by Middle Aged Computer Scientists Extended Macros Are Considered Superfluous Every Mode Accelerates Creation of Software Each Manual's Audience is Completely Stupefied Exceptionally Mediocre Algorithm for Computer Scientists Easily Maintained with the Assistance of Chemical Solutions Eradication of Memory Accomplished with Complete Simplicity
如果只有一个单词，通常取每个音节的首字母：
| cp | CoPy |
| ln | LiNk |
| ls | LiSt |
| mv | MoVe |
| rm | ReMove |
对于目录，通常使用前几个字母作为缩写：
| bin | BINaries |
| dev | DEVices |
| etc | ETCetera |
| lib | LIBrary |
| var | VARiable |
| proc | PROCesses |
| sbin | Superuser BINaries |
| tmp | TeMPorary |
| usr | Unix Shared Resources |
这种缩写的其它情况
| diff | DIFFerences |
| cal | CALendar |
| cat | CATenate |
| ed | EDitor |
| exec | EXECute |
| tab | TABle |
| regexp | REGular EXPression |
如果某种缩写比较深入人心，例如“mesg”代表“message”，在新的复合缩写中，将沿用这种缩写方式
| dmesg | Diagnostic MESsaGe |
| sed | Stream EDitor |
| stty | Set TTY |
| fstab | FileSystem TABle |
| passwd | PASSWorD |
有些缩写中，第一个字母“g”，代表“GNU”
| awk | Aho Weiberger and Kernighan | |
| gawk | GNU AWK | |
| gpg | GNU Privacy Guard | |
| grep | GNU Regular Expression Print | |
| egrep | Extended GREP |
[] 定义中包含自身缩写，如 GNU：
GNU's Not Unix
使用这个定义来解释定义中的缩写：
(GNU's Not Unix)'s Not Unix
这意味着它是可以无限递归的：
(((((GNU's Not Unix)'s Not Unix)'s Not Unix)'s Not Unix)'s Not Unix)'s Not Unix ……