Unix Overview

Kernel
Shell  (csh, tsh, ksh, bsh, bash)
X-windows

Unix Command structure

$ ls    shell looks for an executable in the special collection of directories for executable ls

$ ls  -F     options are specified with a “-“

$ ls > filename   output can be redirected to a file

$ cat < filename  input can be redirected from a file

$ cat < filename > filename

Pipes

output of one program can be sent to another program

$ ls | more

File wildcard characters

*  any string of zero or more characters
?  match any single character
[]  match any of the characters in the []

-->expansion of wildcard characters is done by the shell

Note: the *, and [] are borrowed from a general method of specifying a set of words called regular expressions.

Exaples:  

$ ls *.cpp           list all files that have the extension ".cpp"
$ ls [ab]*.cpp     list all files that start with an "a" or a "b" and have the extension ".cpp"

Common UNIX commands

cd
    change directory, ~ is used to mean your home directory, .. is used to mean the parent of current directory

$ cd                 change to your home directory
$ cd  ~user      change to specified user's home directory   (e.g.   $ cd ~tyson)
$ cd ..              change to the parent of the current directory (the directory above the current directory)
$ cd  112         if "112" is a sub-directory of the current directory, change to it

 
ls
    list the files in the current directory

pwd
    show the current directory (called the path)

mkdir
    make a new directory

$ mkdir 112        make a new directory in the current directory called "112"
$ mkdir ~/112    make a new directory in your home directory called "112"

chmod
    change the protection (access) of a file or directory

rm
    delete a file
    rm -r allows you to delete a directory and everything in it

cp
    copy a file

man       
    show the manual page for a command
          $ man cp

   the -k option searches for keywords in all man pages (useful if you forget the name of a command)
          $ man -k copy
    usually this produces too many matches and they scroll by too fast to read

           $ man -k copy | less

which
          tells you which executable is executed when you type a command
          $ which cp

^C

kill the current process

^D

End of input (end of file) character
When you want to tell a program you are done entering input, type ^D

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