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<TITLE> Useful Unix Commands</TITLE>
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<meta name="description" value=" Useful Unix Commands">
<meta name="keywords" value="unix">
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<P>
<H1>Useful Unix Commands</H1>
<P>
This document gives a few of the most commonly used Unix commands.
These are simple commands that use issue to the computer to do things like
move files or give you information. These are not ``software packages'',
they are much simpler - merely instructions.
</P>
<center><a name="terms"></a>
<h2 align=center>Definitions of Terms</h2>
</a>
</center>
<p>We will need to use the following terms.</p>
<dl>
<ol>
<li>
<dt><b>File</b><dd>A collection of information associated with a file name.
<li>
<dt><b>Directory</b><dd>A name of a collection of files.
<li>
<dt><b>Subdirectory</b><dd>A directory inside a directory.
<li>
<dt><b>Directory tree</b><dd>The name given to the arrangement
of locations of files.
<li>
<dt><b>Path name</b><dd>A sequential naming of all subdirectories
within subdirectories.
</ol>
</dl>
<center>
<h2 align=center>Unix Commands</h2>
</center>
<P id="ls"><a name="ls"></a>
<dl>
<dt><b>ls</b> [ -alt ] [ <i>subname</i> ]
<dd>List files in the current directory and names of any subdirectories.
</dl>
<note><dl><dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% ls </tt> <i> no arguments</i></dt>
<dd>Simply list the files in the current directory.</dd>
<p>
<dt><tt>plato% ls </tt> subname
<dd>When subname is a subdirectory name, you list all the files in the
subdirectory.
<P>
<dt><tt>plato% ls -l</tt>
<dd>List the lone version of the
files which contains information about read/write
permissions and tells which names are directories. Creation times are
also shown.
<P>
<dt><tt>plato% ls -a</tt>
<dd>List ALL files, even the ``hidden''
files that have a name beginning with a dot.
<P>
<note>A good default is ls -aCF. It gives a
multicolumn output for all files.</note>
<P>
<dt><tt>plato% ls -alt</tt>
<dd>gives all information
about all files, -t tell the time when the
files were created and orders files according to that time.
<hr align=left height=4 width=300>
<p><a name="cp"></a>
<dt><b>cp</b>
<dd>Make and identical copy a file.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% cp file.a file.b</tt>
<dd>Copies file.a to create file.b with
all the same information in the
same directory. Two identical files result.
<hr align=left height=4 width=300>
<P><a name="mv"></a>
<dt><b>mv</b>
<dd>Move a file from one location to another.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% mv file.a file.b</tt>
<dd>Move the contents of one file to another. The first ceases to
exist and the second is created and contains the identical
information as the original.
<hr align=left height=4 width=300>
<p><a name="rm"></a>
<dt><b>rm</b>
<dd>Removes (deletes) files.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% rm file.a</tt>
<P>
<note>The option -i asks if the file should be remove. For safety
alias rm with rm -i in your .cshrc file</note>
<dd><hr align=left height=4 width=300>
<P><a name="cat"></a>
<dt><b>cat</b>
<dd>Concatenate files.
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% cat file.a file.b</tt> <b>></b> <tt>file.c</tt>
<dd>This may be a bit technical, but here goes. Cat copies
the standard input into the standard output. In general it
is used as above, to combine two files head to tail, but it
can also be used to edit small files, by giving the cat
command with only one filename. When finished hit control-D.
<hr align=left height=4 width=300>
<P><a name="mkdir"></a>
<dt><b>mkdir</b>
<dd>Make a directory.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% mkdir dirname</tt>
<dd>This would create a subdirectory
named dirname in your current directory (i.e.
the one you were in when you typed the command).
<hr align=left height=4 width=300>
<P><a name="rmdir"></a>
<dt><b>rmdir</b>
<dd>Removes a directory.
<p>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% rmdir dirname</tt>
<dd>This removes an empty directory. if the directory is not empty,
delete existing files first.
<hr align=left height=4 width=300>
<P><a name="cd"></a>
<dt><b>cd</b>
<dd>Change directories.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% cd</tt>
<dd>When used with no arguments, it puts you into the home directory,
i.e., the one you were in when you first logged on.
<P>
<dt><tt>plato% cd dirname</tt>
<dd>This puts you in the subdirectory named dirname.
<hr align=left height=4 width=300>
<P><a name="pwd"></a>
<dt><b>pwd</b>
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% pwd</tt>
<dd>Print working directory. No arguments are required. This tells you
what directory you are in.
<hr align=left height=4 width=300>
<P><a name="printenv"></a>
<dt><b>printenv</b>
<dd>Print the environment variables.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% printenv</tt>
<dd>Environment variable are things that customize
the characteristics of your account. It is not necessary
to change these, but if you want to the command is setenv.
<hr align=left height=4 width=300>
<P><a name="more"></a>
<dt><b>more</b>
<dd>Print the contents of a file to the screen one page at a time.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% more filename</tt>
<dd>This command allows you to page though a file. While paging,
hitting the space bar puts you
on the next page. Hitting q gets you out of more.
<hr align=left height=4 width=300>
<P><a name="grep"></a>
<dt><b>grep</b>
<dd>Search a file for a line contain a particular character string.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% grep string filename</tt>
<dd>This command prints the lines in the file named ''filename``
which contain the characters that you have chosen for the ''string''.
<hr align=left height=4 width=300>
<P><a name="head"></a>
<dt><b>head</b>
<dd>Show the head or first few lines of a file on the screen.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% head filename</tt>
<hr align=left height=4 width=300>
<P><a name="tail"></a>
<dt><b>tail</b>
<dd>Show the tail or last few lines of a file on the screen.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% tail filename</tt>
<hr align=left height=4 width=300>
<P><a name="clear"></a>
<dt><b>clear</b>
<dd>Clear the screen.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt><plato% clear</tt>
<hr align=left height=4 width=300>
<p><a name="diff"></a>
<dt><b>diff</b>
<dd>Show lines of two files which are different.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% diff file1 file2</tt>
<dd>This command prints out the lines in the two files
which are different. Each line is proceeded by a left or
right arrow to indicate the left (file1) or right (file2) file
that it came from.
<hr align=left height=4 width=300>
<P><a name="man"></a>
<dt><b>man</b>
<dd>Like a help command, but give the manual
pages explaining Unix commands
in detail.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% man cmdname</tt>
<dd>Here, cmdname id the name of the command that you want to know about.
<hr align=left height=4 width=300>
<P><a name="logout"></a>
<dt><b>logout</b>
<dd>Last command you type to leave the system entirely.
<P>
<dt>U<font size=-1>SAGE</font>:
<dt><tt>plato% logout</tt>
</UL>
<P>
These commands allow you to move around in the file system and look at what
you have and make changes in it. These are the commands that you
need to use between time that you are running a program or piece of
software.
<P>
<P><ADDRESS>
</ADDRESS>
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