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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 45] 45.6 Making Sure Your Script Runs with Bourne Shell, Without #! </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="1998-08-04T21:54:25Z"><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="ch45_01.htm"TITLE="45. Shell Programming for the Initiated"><LINKREL="prev"HREF="ch45_05.htm"TITLE="45.5 A File That Shows Itself... and What #! Does "><LINKREL="next"HREF="ch45_07.htm"TITLE="45.7 The exec 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="ch45_05.htm"TITLE="45.5 A File That Shows Itself... and What #! Does "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 45.5 A File That Shows Itself... and What #! Does "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 45<BR>Shell Programming for the Initiated</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch45_07.htm"TITLE="45.7 The exec Command "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 45.7 The exec Command "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0215">45.6 Making Sure Your Script Runs with Bourne Shell, Without #! </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-52528"></A><ACLASS="indexterm"NAME="AUTOID-52531"></A><ACLASS="indexterm"NAME="AUTOID-52534"></A><ACLASS="indexterm"NAME="AUTOID-52537"></A>Lots of UNIX versions let you start a script file this way:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen"><ACLASS="indexterm"NAME="AUTOID-52542"></A>#!/bin/sh</PRE></BLOCKQUOTE></P><PCLASS="para">That executable file will always be read by a Bourne shell. If someversions of UNIX you use don't<SPANCLASS="link">understand <CODECLASS="literal">#!</CODE> (<ACLASS="linkend"HREF="ch44_04.htm"TITLE="Testing How Your System Executes Files ">44.4</A>)</SPAN>,here's how to start your scripts:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"> <ACLASS="co"HREF="ch44_09.htm"TITLE="44.9 Testing Your Success ">||</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">#!/bin/shexport PATH || exec /bin/sh $0 $argv:q</PRE></TD></TR></TABLE></P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-52552"></A>If a Bourne shell reads that line (that is, if the <CODECLASS="literal">#!/bin/sh</CODE>succeeded), the <CODECLASS="literal">export</CODE> <CODECLASS="literal">PATH</CODE> command will succeed andthe rest of the command line will be skipped. If a C shell reads theline, it will print the error <CODECLASS="literal">export: Command not found</CODE>. Thenit will run <CODECLASS="literal">exec /bin/sh $0 $argv:q</CODE>. The<SPANCLASS="link"><EMCLASS="emphasis">exec</EM> (<ACLASS="linkend"HREF="ch45_07.htm"TITLE="The exec Command ">45.7</A>)</SPAN>replaces the C shell with a Bourne shell, passes it the name of thescript file in <CODECLASS="literal">$0</CODE>, and passes a quoted list of thecommand-line arguments from <CODECLASS="literal">$argv</CODE><SPANCLASS="link"><CODECLASS="literal">:q</CODE> (<ACLASS="linkend"HREF="ch09_06.htm"TITLE="String Editing (Colon) Operators ">9.6</A>)</SPAN>.</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="ch45_05.htm"TITLE="45.5 A File That Shows Itself... and What #! Does "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 45.5 A File That Shows Itself... and What #! 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