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<HTML><HEAD><TITLE>Recipe 7.4. Making Perl Report Filenames in Errors (Perl Cookbook)</TITLE><METANAME="DC.title"CONTENT="Perl Cookbook"><METANAME="DC.creator"CONTENT="Tom Christiansen & Nathan Torkington"><METANAME="DC.publisher"CONTENT="O'Reilly & Associates, Inc."><METANAME="DC.date"CONTENT="1999-07-02T01:36:07Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-243-3"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="ch07_01.htm"TITLE="7. File Access"><LINKREL="prev"HREF="ch07_04.htm"TITLE="7.3. Expanding Tildes in Filenames"><LINKREL="next"HREF="ch07_06.htm"TITLE="7.5. Creating Temporary Files"></HEAD><BODYBGCOLOR="#FFFFFF"><img alt="Book Home" border="0" src="gifs/smbanner.gif" usemap="#banner-map" /><map name="banner-map"><area shape="rect" coords="1,-2,616,66" href="index.htm" alt="Perl Cookbook"><area shape="rect" coords="629,-11,726,25" href="jobjects/fsearch.htm" alt="Search this book" /></map><div class="navbar"><p><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch07_04.htm"TITLE="7.3. Expanding Tildes in Filenames"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 7.3. Expanding Tildes in Filenames"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1"><ACLASS="chapter"REL="up"HREF="ch07_01.htm"TITLE="7. File Access"></A></FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch07_06.htm"TITLE="7.5. Creating Temporary Files"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 7.5. Creating Temporary Files"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch07-42527">7.4. Making Perl Report Filenames in Errors</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch07-pgfId-508">Problem<ACLASS="indexterm"NAME="ch07-idx-1000009600-0"></A><ACLASS="indexterm"NAME="ch07-idx-1000009600-1"></A><ACLASS="indexterm"NAME="ch07-idx-1000009600-2"></A></A></H3><PCLASS="para">Your program works with files, but Perl's errors and warnings only report the last used filehandle, not the name of the file.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch07-pgfId-514">Solution</A></H3><PCLASS="para">Use the filename as the filehandle:</P><PRECLASS="programlisting">open($path, "< $path") or die "Couldn't open $path for reading : $!\n";</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch07-pgfId-524">Discussion</A></H3><PCLASS="para">Ordinarily, error messages say:</P><PRECLASS="programlisting"><CODECLASS="userinput"><B><CODECLASS="replaceable"><I>Argument "3\n" isn't numeric in multiply at tallyweb line 16, <LOG> chunk 17.</I></CODE></B></CODE></PRE><PCLASS="para">The filehandle LOG doesn't help much because you don't know which file the handle was connected to. By using the filename itself as indirect filehandle, Perl produces more informative errors and warnings:</P><PRECLASS="programlisting"><CODECLASS="userinput"><B><CODECLASS="replaceable"><I>Argument "3\n" isn't numeric in multiply at tallyweb</I></CODE></B></CODE><CODECLASS="userinput"><B><CODECLASS="replaceable"><I> line 16, </usr/local/data/mylog3.dat> chunk 17.</I></CODE></B></CODE></PRE><PCLASS="para">Unfortunately, this doesn't work with <CODECLASS="literal">strict</CODE> <CODECLASS="literal">refs</CODE> turned on because the variable <CODECLASS="literal">$path</CODE> doesn't really have a filehandle in it, but just a string that sometimes behaves as one. The chunk mentioned in warnings and error messages is the current value of the <CODECLASS="literal">$.</CODE> variable. <ACLASS="indexterm"NAME="ch07-idx-1000009602-0"></A><ACLASS="indexterm"NAME="ch07-idx-1000009602-1"></A><ACLASS="indexterm"NAME="ch07-idx-1000009602-2"></A></P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch07-pgfId-540">See Also</A></H3><PCLASS="para"><ACLASS="xref"HREF="ch07_02.htm"TITLE="Opening a File">Recipe 7.1</A>; the <CODECLASS="literal">open</CODE> function in <ICLASS="filename">perlfunc </I>(1) and <ACLASS="olink"HREF="../prog/ch03_01.htm">Chapter 3</A> of <ACLASS="citetitle"HREF="../prog/index.htm"TITLE="Programming Perl"><CITECLASS="citetitle">Programming Perl</CITE></A></P></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="684"TITLE="footer"><TABLEWIDTH="684"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch07_04.htm"TITLE="7.3. Expanding Tildes in Filenames"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 7.3. Expanding Tildes in Filenames"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><ACLASS="book"HREF="index.htm"TITLE="Perl Cookbook"><IMGSRC="../gifs/txthome.gif"ALT="Perl Cookbook"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch07_06.htm"TITLE="7.5. Creating Temporary Files"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 7.5. Creating Temporary Files"BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228">7.3. Expanding Tildes in Filenames</TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><ACLASS="index"HREF="index/index.htm"TITLE="Book Index"><IMGSRC="../gifs/index.gif"ALT="Book Index"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228">7.5. 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