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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 51] 51.9 Making a "Login" Shell</TITLE><METANAME="DC.title"CONTENT="UNIX Power Tools"><METANAME="DC.creator"CONTENT="Jerry Peek, Tim O'Reilly & Mike Loukides"><METANAME="DC.publisher"CONTENT="O'Reilly & Associates, Inc."><METANAME="DC.date"CONTENT="1998-08-04T21:57:27Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-260-3"SCHEME="ISBN"><METANAME="DC.language"CONTENT="en-US"><METANAME="generator"CONTENT="Jade 1.1/O'Reilly DocBook 3.0 to HTML 4.0"><LINKREV="made"HREF="mailto:online-books@oreilly.com"TITLE="Online Books Comments"><LINKREL="up"HREF="ch51_01.htm"TITLE="51. Miscellaneous Useful Programs and Curiosities"><LINKREL="prev"HREF="ch51_08.htm"TITLE="51.8 Type Bang Splat. Don't Forget the Rabbit Ears "><LINKREL="next"HREF="ch51_10.htm"TITLE="51.10 The date Command "></HEAD><BODYBGCOLOR="#FFFFFF"TEXT="#000000"><DIVCLASS="htmlnav"><H1><IMGSRC="gifs/smbanner.gif"ALT="UNIX Power Tools"USEMAP="#srchmap"BORDER="0"></H1><MAPNAME="srchmap"><AREASHAPE="RECT"COORDS="0,0,466,58"HREF="index.htm"ALT="UNIX Power Tools"><AREASHAPE="RECT"COORDS="467,0,514,18"HREF="jobjects/fsearch.htm"ALT="Search this book"></MAP><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch51_08.htm"TITLE="51.8 Type Bang Splat. Don't Forget the Rabbit Ears "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 51.8 Type Bang Splat. Don't Forget the Rabbit Ears "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 51<BR>Miscellaneous Useful Programs and Curiosities</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch51_10.htm"TITLE="51.10 The date Command "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 51.10 The date Command "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0193">51.9 Making a "Login" Shell</A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-60376"></A><ACLASS="indexterm"NAME="AUTOID-60378"></A>When you log in to most UNIX systems, your shell is a <EMCLASS="emphasis">login shell</EM>.When a shell is a login shell, it acts differently.For example, the shell reads a special<SPANCLASS="link">setup file (<ACLASS="linkend"HREF="ch02_02.htm"TITLE="Shell Setup Files-Which, Where, and Why ">2.2</A>)</SPAN>like <EMCLASS="emphasis">.profile</EM> or <EMCLASS="emphasis">.login</EM>.UNIX "knows" how to tell the shells to be login shells.If you type the shell's name (like <EMCLASS="emphasis">sh</EM> or <EMCLASS="emphasis">/bin/csh</EM>) at a prompt,that will not start a login shell.</P><PCLASS="para">Sometimes, when you're testing an account or using a window system,you want to start a login shell without logging in.UNIX shells act like login shells when they are executed with a name thatstarts with a dash (<CODECLASS="literal">-</CODE>).[1]The easiest way to do this, which wastes a lot of disk space (and may notwork on your system anyway if the shells are read-protected), is to makeyour own copy of the shell and name it starting with a dash:</P><BLOCKQUOTECLASS="footnote"><PCLASS="para">[1] <EMCLASS="emphasis">bash</EM> also has a command-line option, <EMCLASS="emphasis">-login</EM>, that makes itact like a login shell.</P></BLOCKQUOTE><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"><ACLASS="co"HREF="ch04_02.htm"TITLE="4.2 A bin Directory for Your Programs and Scripts ">bin</A> <ACLASS="co"HREF="ch23_14.htm"TITLE="23.14 Handling a Filename Starting with a Dash (-) ">./-</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">$ <CODECLASS="userinput"><B>cd $HOME/bin</B></CODE>$ <CODECLASS="userinput"><B>cp /bin/csh ./-csh</B></CODE></PRE></TD></TR></TABLE></P><PCLASS="para">It's better to make a<SPANCLASS="link">symbolic link (<ACLASS="linkend"HREF="ch18_04.htm"TITLE="More About Links ">18.4</A>)</SPAN>to the shell:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">$ <CODECLASS="userinput"><B>cd $HOME/bin</B></CODE>$ <CODECLASS="userinput"><B>ln -s /bin/csh ./-csh</B></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">(Or, if your own <EMCLASS="emphasis">bin</EM> subdirectory is on the same filesystem as<EMCLASS="emphasis">/bin</EM>, you can use a<SPANCLASS="link">hard link (<ACLASS="linkend"HREF="ch18_04.htm"TITLE="More About Links ">18.4</A>)</SPAN>.)A third way is to write a little<SPANCLASS="link">C program (<ACLASS="linkend"HREF="ch52_08.htm"TITLE="Building Programs from Source Code ">52.8</A>)</SPAN>that runs the actual shell but tells the shell that its namestarts with a dash.This is how the UNIX login process does it:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">main(){ execl("/bin/csh", "-csh", 0);}</PRE></BLOCKQUOTE></P><PCLASS="para">No matter which way you choose, you can execute your new shell by typing itsname:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">$ <CODECLASS="userinput"><B>-csh</B></CODE> <ICLASS="lineannotation">...normal C shell login process...</I>% <ICLASS="lineannotation">...run whatever commands you want...</I>% <CODECLASS="userinput"><B>logout</B></CODE>$ <ICLASS="lineannotation">...back to original shell</I></PRE></BLOCKQUOTE></P><PCLASS="para">Article<ACLASS="xref"HREF="ch02_16.htm"TITLE="Approved Shells: Using Unapproved Login Shell ">2.16</A>shows how this can be used to change your normal login shell.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">JP</SPAN></P></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="515"TITLE="footer"><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch51_08.htm"TITLE="51.8 Type Bang Splat. 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