Two-Character Unix Commands

Here’s a fun survey question: name as many two-character Unix commands as you can and say what they do.

Let’s be precise about what we mean by a “command”:

• Shell aliases like la are not commands.
• Shell built-in commands count as commands; over time the shell incorporated directly things that were previously separate executables in Unix.
• Commands not available in a wide variety of Unix distributions by default don’t count. In other words, if you have to install some optional package to get the command then it isn’t a “Unix” command.
• Optional: Only allow commands included in a “classic” Unix from Bell Labs.

Ready? Let’s go.

Command	Description
ar	Archive librarian
as	Assembler
at	Execute commands at a later time
bc	Arbitrary precision calculator
bg	Run suspended command in the background
cc	C compiler
cd	Change directory
cp	Copy files
dc	Desk calculator
dd	Convert and copy files
df	Disk free space
du	Disk usage
ed	Line-oriented editor
ex	Extended line-oriented editor
fg	Resume suspended command in the foreground
ln	Make soft links
lp	Print files
ls	List files
m4	Macro processor
mt	Magnetic tape control
mv	Move files
nl	Number lines
nm	Dump symbol table information
od	Octal dump
pr	Prepare files for printing
ps	Process status
rm	Remove files
sh	Shell
su	Super user
tr	Translate characters
ul	Underlining
vi	Visual editor
wc	Word count