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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 2] 2.8 Identifying Login Shells </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="1998-08-04T21:32:06Z"><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="ch02_01.htm"TITLE="2. Logging In"><LINKREL="prev"HREF="ch02_07.htm"TITLE="2.7 C Shell Setup Files Aren't Read When You Want Them to Be? "><LINKREL="next"HREF="ch02_09.htm"TITLE="2.9 Speeding Up Your C Shell with set prompt Test "></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="ch02_07.htm"TITLE="2.7 C Shell Setup Files Aren't Read When You Want Them to Be? "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 2.7 C Shell Setup Files Aren't Read When You Want Them to Be? "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 2<BR>Logging In</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch02_09.htm"TITLE="2.9 Speeding Up Your C Shell with set prompt Test "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 2.9 Speeding Up Your C Shell with set prompt Test "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0252">2.8 Identifying Login Shells </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-3227"></A><ACLASS="indexterm"NAME="AUTOID-3230"></A>When you first log in to a UNIX system from a terminal, thesystem usually starts a <EMCLASS="emphasis">login shell</EM>. This is where you want todo general setup - initialize your terminal, set environment variables,and so on. Here the C shell reads your <EMCLASS="emphasis">.login</EM> file, andBourne-type shells read <EMCLASS="emphasis">.profile</EM> (<EMCLASS="emphasis">bash</EM> can read others).<ACLASS="indexterm"NAME="AUTOID-3236"></A><ACLASS="indexterm"NAME="AUTOID-3238"></A><ACLASS="indexterm"NAME="AUTOID-3240"></A></P><PCLASS="para">Other shells are either<SPANCLASS="link">subshells (<ACLASS="linkend"HREF="ch38_04.htm"TITLE="Subshells ">38.4</A>)</SPAN>(started from the login shell)or separate shells started by<SPANCLASS="link"><EMCLASS="emphasis">at</EM> (<ACLASS="linkend"HREF="ch40_03.htm"TITLE="The at Command ">40.3</A>)</SPAN>,<SPANCLASS="link"><EMCLASS="emphasis">rsh</EM> (<ACLASS="linkend"HREF="ch01_33.htm"TITLE="UNIX Networking and Communications ">1.33</A>)</SPAN>,etc. These shells don't read <EMCLASS="emphasis">.login</EM> or<EMCLASS="emphasis">.profile</EM>.</P><PCLASS="para">To make it possible to find out which you've got, add theline below to the top of your <EMCLASS="emphasis">.login</EM> or <EMCLASS="emphasis">.profile</EM> file:The line sets a<SPANCLASS="link">shell variable (<ACLASS="linkend"HREF="ch06_08.htm"TITLE="Shell Variables ">6.8</A>)</SPAN>named <EMCLASS="emphasis">loginshell</EM>:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">set loginshell=yes <ICLASS="lineannotation">...csh</I>loginshell=yes <ICLASS="lineannotation">...sh-type shells</I></PRE></BLOCKQUOTE></P><PCLASS="para">Now wherever you need to know the type of shell, use tests like:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"><ACLASS="co"HREF="ch47_03.htm"TITLE="47.3 Conditional Statements with if ">if</A> <ACLASS="co"HREF="ch47_04.htm"TITLE="47.4 C Shell Variable Operators and Expressions ">$?</A> <ACLASS="co"HREF="ch44_08.htm"TITLE="44.8 Test Exit Status with the if Statement ">if</A> <ACLASS="co"HREF="ch47_04.htm"TITLE="47.4 C Shell Variable Operators and Expressions ">[...]</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">if ($?loginshell) <ICLASS="lineannotation">...csh</I>if [ -n "$loginshell" ] <ICLASS="lineannotation">...sh-type shells</I></PRE></TD></TR></TABLE></P><PCLASS="para">This works because only login shells read <EMCLASS="emphasis">.login</EM> or<EMCLASS="emphasis">.profile</EM>. The <EMCLASS="emphasis">loginshell</EM> variable will be defined onlyin login shells.</P><PCLASS="para">Article<ACLASS="xref"HREF="ch07_09.htm"TITLE="Show Subshell Level with $SHLVL ">7.9</A>shows another solution.</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="ch02_07.htm"TITLE="2.7 C Shell Setup Files Aren't Read When You Want Them to Be? "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 2.7 C Shell Setup Files Aren't Read When You Want Them to Be? 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