大概是个博客

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[3]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