CMPSC 311 - Unix Commands

Hierachrial File System - Directory Tree

• Root

• Home

• Standard

Standard directory

• /etc: configuration files

• /dev: device files

• /home: user home directories

• /lib: shared library files used by core systems programs

• /sbin: system binaries for vital system tasks

• /usr: programs and support files for users

• /var: system log files

Types of shell commands

• binary files: separate programs executed by the shell

• shell builtins: commands interpreted by the shell; the functionality for these commands is implemented in the shell program itself

• aliases: shortcuts defined by users to avoid typing long commands or command sequences     

Shell Variables

Variables that a user can set to control the shell's behavior

• PATH: when a user types a command, the shell looks for the binary in the list of directories present in the PATH variable.    

Input/Output Redirection (3 streams)

• standard input: where the program reads the input from; attached to the keyboard by default

• standard output: where the program writes its output, attached to the screen by default

• standard error: where the program writes its errors; attached to screen by default   

>

Redirect standard output to a file

»

Append standard output to a file

2>

Redirect standard error to a file

<

Read input from a file instead of keyboard

|

Pipe command. Inputs an output of a command to another command

Ex: [command1] | [command2]

man <command>

Provides details of the command 

pwd

Print the pathname of the current directory 

ls

List the files and subdirectories in a directory

cd <directory>

Change directories

cp <file> <file2>

Copy the contents of file into file2

history

List history of all commands issued at system prompt

mv <file> <file2>

Copy file to file2 (file2 replaced)

rm <file>

Remove or delete files

mkdir <dir>

Make a directory

rmdir <dir>

Remove a directory

type

Display information about command type.

alias

Create an alias, aliases allow a string to be substituted for a word when it is used as the first word of a simple command.

echo

display a line of text

cat <files>

Print contents of file in the command window

ls -a

List all the files in a directory including dot files