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<html><head><title>Common Features (UNIX in a Nutshell: System V Edition)</title><link rel="stylesheet" type="text/css" href="../style/style1.css" /><meta name="DC.Creator" content="Arnold Robbins" /><meta name="DC.Format" content="text/xml" scheme="MIME" /><meta name="DC.Language" content="en-US" /><meta name="DC.Publisher" content="O'Reilly & Associates, Inc." /><meta name="DC.Source" scheme="ISBN" content="1-56592-427-4" /><meta name="DC.Subject.Keyword" content="stuff" /><meta name="DC.Title" content="UNIX in a Nutshell: System V Edition" /><meta name="DC.Type" content="Text.Monograph" /></head><body bgcolor="#ffffff"><img src="gifs/smbanner.gif" usemap="#banner-map" border="0" alt="Book Home" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Book Title" /><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch03_03.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228" /><td align="right" valign="top" width="228"><a href="ch03_05.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr></table></div><h2 class="sect1">3.4. Common Features</h2><p><a name="ch03.shellfeature1" /><a name="ch03.shellfeature2" /><a name="ch03.shellfeature3" />The following table displaysfeatures that are common to the Bourne, Korn, and C shells.Note that the Korn shell is an enhanced version of the Bourne shell;therefore, the Korn shell includes all features of the Bourne shell,plus some others. The commands <tt class="literal">bg</tt>, <tt class="literal">fg</tt>,<tt class="literal">jobs</tt>,<tt class="literal">stop</tt>,and <tt class="literal">suspend</tt> are available only on systems thatsupport job control. (Essentially all modern Unix systems do.)</p><table border="1" cellpadding="3"><tr><th><em class="emphasis">Symbol/Command</em></th><th><em class="emphasis">Meaning/Action</em></th></tr><tr><td><tt class="literal">></tt></td><td>Redirect output.</td></tr><tr><td><tt class="literal">>></tt></td><td>Append to file.</td></tr><tr><td><tt class="literal"><</tt></td><td>Redirect input.</td></tr><tr><td><tt class="literal"><<</tt></td><td>“Here” document (redirect input).</td></tr><tr><td><tt class="literal">|</tt></td><td>Pipe output.</td></tr><tr><td><tt class="literal">|&</tt></td><td>Start a coprocess. Korn shell only.</td></tr><tr><td><tt class="literal">&</tt></td><td>Run process in background.</td></tr><tr><td><tt class="literal">;</tt></td><td>Separate commands on same line.</td></tr><tr><td><tt class="literal">*</tt></td><td>Match any character(s) in filename.</td></tr><tr><td><tt class="literal">?</tt></td><td>Match single character in filename.</td></tr><tr><td><tt class="literal">[ ]</tt></td><td>Match any characters enclosed.</td></tr><tr><td><tt class="literal">( )</tt></td><td>Execute in subshell.</td></tr><tr><td><tt class="literal">‘ ‘</tt></td><td>Substitute output of enclosed command.</td></tr><tr><td><tt class="literal">" "</tt></td><td>Partial quote (allows variable and command expansion).</td></tr><tr><td><tt class="literal">' '</tt></td><td>Full quote (no expansion).</td></tr><tr><td><tt class="literal">\</tt></td><td>Quote following character.</td></tr><tr><td><tt class="literal">$</tt><em class="replaceable"><tt>var</tt></em></td><td>Use value for variable.</td></tr><tr><td><tt class="literal">$$</tt></td><td>Process ID.</td></tr><tr><td><tt class="literal">$0</tt></td><td>Command name.</td></tr><tr><td><tt class="literal">$</tt><em class="replaceable"><tt>n</em></td><td><em class="emphasis">n</em>th argument (0 <img src="figs/le.gif" alt="Figure " /> <em class="emphasis">n</tt></em> <img src="figs/le.gif" alt="Figure " /> 9).</td></tr><tr><td><tt class="literal">$*</tt></td><td>All arguments as simple words.</td></tr><tr><td><tt class="literal">#</tt></td><td>Begin comment.</td></tr><tr><td><tt class="literal">bg</tt></td><td>Background execution.</td></tr><tr><td><tt class="literal">break</tt></td><td>Break from loop statements.</td></tr><tr><td><tt class="literal">cd</tt></td><td>Change directory.</td></tr><tr><td><tt class="literal">continue</tt></td><td>Resume a program loop.</td></tr><tr><td><tt class="literal">echo</tt></td><td>Display output.</td></tr><tr><td><tt class="literal">eval</tt></td><td>Evaluate arguments.</td></tr><tr><td><tt class="literal">exec</tt></td><td>Execute a new shell.</td></tr><tr><td><tt class="literal">fg</tt></td><td>Foreground execution.</td></tr><tr><td><tt class="literal">jobs</tt></td><td>Show active jobs.</td></tr><tr><td><tt class="literal">kill</tt></td><td>Terminate running jobs.</td></tr><tr><td><tt class="literal">shift</tt></td><td>Shift positional parameters.</td></tr><tr><td><tt class="literal">stop</tt></td><td>Suspend a background job.</td></tr><tr><td><tt class="literal">suspend</tt></td><td>Suspend a foreground job (such as a shell created by <tt class="literal">su</tt>).</td></tr><tr><td><tt class="literal">time</tt></td><td>Time a command.</td></tr><tr><td><tt class="literal">umask</tt></td><td>Set default file permissions for new files.</td></tr><tr><td><tt class="literal">unset</tt></td><td>Erase variable or function definitions.</td></tr><tr><td><tt class="literal">wait</tt></td><td>Wait for a background job to finish.</td></tr></table><p><hr width="684" align="left" /><div class="navbar"><table width="684" border="0"><tr><td align="left" valign="top" width="228"><a href="ch03_03.htm"><img src="../gifs/txtpreva.gif" alt="Previous" border="0" /></a></td><td align="center" valign="top" width="228"><a href="index.htm"><img src="../gifs/txthome.gif" alt="Home" border="0" /></a></td><td align="right" valign="top" width="228"><a href="ch03_05.htm"><img src="../gifs/txtnexta.gif" alt="Next" border="0" /></a></td></tr><tr><td align="left" valign="top" width="228">3.3. Shell Flavors</td><td align="center" valign="top" width="228"><a href="index/index.htm"><img src="../gifs/index.gif" alt="Book Index" border="0" /></a></td><td align="right" valign="top" width="228">3.5. Differing Features</td></tr></table></div><hr width="684" align="left" /><img src="../gifs/navbar.gif" usemap="#library-map" border="0" alt="Library Navigation Links" /><p><p><font size="-1"><a href="copyrght.htm">Copyright © 2003</a> O'Reilly & Associates. 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