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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 8] 8.17 verbose and echo Variables Show Quoting </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="1998-08-04T21:34:34Z"><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="ch08_01.htm"TITLE="8. How the Shell Interprets What You Type"><LINKREL="prev"HREF="ch08_16.htm"TITLE="8.16 Quoting Handles Special Characters in Filenames "><LINKREL="next"HREF="ch08_18.htm"TITLE="8.18 Here Documents "></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="ch08_16.htm"TITLE="8.16 Quoting Handles Special Characters in Filenames "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 8.16 Quoting Handles Special Characters in Filenames "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 8<BR>How the Shell Interprets What You Type</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch08_18.htm"TITLE="8.18 Here Documents "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 8.18 Here Documents "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-7796">8.17 verbose and echo Variables Show Quoting </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-8790"></A>The C shell has two<SPANCLASS="link">variables (<ACLASS="linkend"HREF="ch06_09.htm"TITLE="Special C Shell Variables ">6.9</A>)</SPAN>that, when set, will help you follow theconvoluted trail of variable and metacharacter expansion.This will echo every command line before shell variableshave been evaluated:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"><ACLASS="co"HREF="ch06_08.htm"TITLE="6.8 Shell Variables ">set</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen">% <CODECLASS="userinput"><B>set verbose</B></CODE></PRE></TD></TR></TABLE></P><PCLASS="para">This command will display each line after the variables andmetacharacters have been substituted:<ACLASS="indexterm"NAME="AUTOID-8798"></A></P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>set echo</B></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">If you wish to turn the variables off, use<SPANCLASS="link"><EMCLASS="emphasis">unset</EM> (<ACLASS="linkend"HREF="ch06_08.htm"TITLE="Shell Variables ">6.8</A>)</SPAN>instead of<EMCLASS="emphasis">set</EM>.</P><PCLASS="para">The Bourne shell syntax is different.To turn on the verbose flag, use:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">$ <CODECLASS="userinput"><B>set -v</B></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">The command <CODECLASS="literal">set</CODE> <CODECLASS="literal">-x</CODE> turns on the echo flag.You can also type them together: <CODECLASS="literal">set</CODE> <CODECLASS="literal">-xv</CODE>.</P><PCLASS="para">If your version of UNIX<SPANCLASS="link">understands (<ACLASS="linkend"HREF="ch44_04.htm"TITLE="Testing How Your System Executes Files ">44.4</A>)</SPAN><ACLASS="indexterm"NAME="AUTOID-8818"></A><ACLASS="indexterm"NAME="AUTOID-8821"></A><ACLASS="indexterm"NAME="AUTOID-8824"></A><ACLASS="indexterm"NAME="AUTOID-8827"></A>scripts that start with <CODECLASS="literal">#!</CODE>,here's a convenient way to turn these variables on from the first line of a script:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">#!/bin/sh -xv</PRE></BLOCKQUOTE></P><PCLASS="para">It is not necessary to modify the program.You can enable variable tracing in Bourne shell scripts by typing theshell name and options on the command line:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">$ <CODECLASS="userinput"><B>sh -v </B></CODE><CODECLASS="replaceable"><I>script</I></CODE>$ <CODECLASS="userinput"><B>sh -x </B></CODE><CODECLASS="replaceable"><I>script</I></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">Not all Bourne shells let you turn these variables off.If yours does, you can do it by using a plus sign instead of a minus sign:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">set +xv</PRE></BLOCKQUOTE></P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">BB</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="ch08_16.htm"TITLE="8.16 Quoting Handles Special Characters in Filenames "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 8.16 Quoting Handles Special Characters in Filenames "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><ACLASS="book"HREF="index.htm"TITLE="UNIX Power Tools"><IMGSRC="gifs/txthome.gif"SRC="gifs/txthome.gif"ALT="UNIX Power 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