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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 16] 16.14 Showing Non-Printable Characters in Filenames </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="1998-08-04T21:37:47Z"><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="ch16_01.htm"TITLE="16. Where Did I Put That?"><LINKREL="prev"HREF="ch16_13.htm"TITLE="16.13 Can't Access a File? Look for Spaces in the Name "><LINKREL="next"HREF="ch16_15.htm"TITLE="16.15 Script with a :-) for UNIX Converts: dir, ..., ... "></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="ch16_13.htm"TITLE="16.13 Can't Access a File? Look for Spaces in the Name "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 16.13 Can't Access a File? Look for Spaces in the Name "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 16<BR>Where Did I Put That?</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch16_15.htm"TITLE="16.15 Script with a :-) for UNIX Converts: dir, ..., ... "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 16.15 Script with a :-) for UNIX Converts: dir, ..., ... "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-7550">16.14 Showing Non-Printable Characters in Filenames </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-17332"></A><ACLASS="indexterm"NAME="AUTOID-17335"></A><ACLASS="indexterm"NAME="AUTOID-17338"></A><ACLASS="indexterm"NAME="AUTOID-17342"></A><ACLASS="indexterm"NAME="AUTOID-17346"></A><ACLASS="indexterm"NAME="AUTOID-17349"></A>From timeto time, you may get files with non-printing characters, spaces, andother garbage in them. This usually is the result of somemistake - but it's a pain nevertheless.</P><PCLASS="para">If you're using BSD UNIX, the <EMCLASS="emphasis">ls</EM> command gives you some help; itwill convert all non-printing characters to a question mark (<CODECLASS="literal">?</CODE>), givingyou some idea that something funny is there.[2]For example:</P><BLOCKQUOTECLASS="footnote"><PCLASS="para">[2] The <EMCLASS="emphasis">-q</EM> option is the default only when <EMCLASS="emphasis">ls</EM>'s standard outputis a terminal.If you pipe the output or redirect it to a file, remember to add <EMCLASS="emphasis">-q</EM>.</P></BLOCKQUOTE><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>ls</B></CODE>ab??cd</PRE></BLOCKQUOTE></P><PCLASS="para">This shows that there are two non-printing characters between <CODECLASS="literal">ab</CODE> and<CODECLASS="literal">cd</CODE>. To delete (or rename) this file, you can use a wildcardpattern like <EMCLASS="emphasis">ab??cd</EM>.</P><BLOCKQUOTECLASS="note"><PCLASS="para"><STRONG>NOTE:</STRONG> BE CAREFUL. When I was new to UNIX, I once accidentallygenerated a lot of weird filenames.<EMCLASS="emphasis">ls</EM> told me that they allbegan with <EMCLASS="emphasis">????</EM>,so I naively typed <CODECLASS="literal">rm ????*</CODE>.That's when my troubles began.See article<ACLASS="xref"HREF="ch23_02.htm"TITLE="rm and Its Dangers ">23.2</A>for the rest of the gruesome story.(I spent the next day and night trying to undo the damage.)THE MORAL IS: It's always a goodidea to use <EMCLASS="emphasis">echo</EM> to test filenames with wildcards in them.</P></BLOCKQUOTE><PCLASS="para"> If you're using System V UNIX, you have a different set of problems.System V's <EMCLASS="emphasis">ls</EM> doesn't convert the non-printing characters toquestion marks. In fact, it doesn't do anything at all - it just spitsthese weird characters at your terminal, which can respond in anynumber of strange and hostile ways. Most of the non-printingcharacters have special meanings - ranging from "don't take any moreinput" to "clear the screen."</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-17377"></A>To prevent this, use the <EMCLASS="emphasis">-b</EM> option.[3]This tells <EMCLASS="emphasis">ls</EM> toprint the octal value of any non-printing characters, preceeded by abackslash. For example, on System V:</P><BLOCKQUOTECLASS="footnote"><PCLASS="para">[3] On BSD, pipe the <EMCLASS="emphasis">ls -q</EM> output through<SPANCLASS="link"><EMCLASS="emphasis">cat -v</EM> or <EMCLASS="emphasis">od -c</EM> (<ACLASS="linkend"HREF="ch25_07.htm"TITLE="Show Non-Printing Characters with cat -v or od -c ">25.7</A>)</SPAN>to see what the non-printing characters are.</P></BLOCKQUOTE><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>ls -b</B></CODE>ab\013\014cd</PRE></BLOCKQUOTE></P><PCLASS="para">This shows that the non-printing characters have octal values 13 and14, respectively. If you look up these values in an<SPANCLASS="link">ASCII table (<ACLASS="linkend"HREF="ch51_03.htm"TITLE="ASCII Characters: Listing and Getting Values ">51.3</A>)</SPAN>,you will see that they correspond to CTRL-k and CTRL-l. And - if youthink about what's happening - you'll realize that CTRL-l is aformfeed character, which tells many terminals to clear the screen.That's why the regular <EMCLASS="emphasis">ls</EM> command behaved so strangely.</P><PCLASS="para">Once you know what you're dealing with, you can use a wildcardpattern to delete or rename the file.</P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">ML</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="ch16_13.htm"TITLE="16.13 Can't Access a File? Look for Spaces in the Name "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 16.13 Can't Access a File? 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