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<HTML><HEAD><TITLE>Recipe 7.3. Expanding Tildes in Filenames (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="1999-07-02T01:36:06Z"><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_03.htm"TITLE="7.2. Opening Files with Unusual Filenames"><LINKREL="next"HREF="ch07_05.htm"TITLE="7.4. Making Perl Report Filenames in Errors"></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_03.htm"TITLE="7.2. Opening Files with Unusual Filenames"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 7.2. Opening Files with Unusual 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_05.htm"TITLE="7.4. Making Perl Report Filenames in Errors"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 7.4. Making Perl Report Filenames in Errors"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch07-chap07_expanding_0">7.3. Expanding Tildes in Filenames</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch07-pgfId-1000008545">Problem<ACLASS="indexterm"NAME="ch07-idx-1000009594-0"></A><ACLASS="indexterm"NAME="ch07-idx-1000009594-1"></A><ACLASS="indexterm"NAME="ch07-idx-1000009594-2"></A></A></H3><PCLASS="para">You want to open filenames like <EMCLASS="emphasis">~username/blah</EM>, but <CODECLASS="literal">open</CODE> doesn't interpret the tilde to mean a home directory.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch07-pgfId-460">Solution</A></H3><PCLASS="para">Expand the filename manually with a substitution:</P><PRECLASS="programlisting">$filename =~ s{ ^ ~ ( [^/]* ) } { $1 ? (getpwnam($1))[7] : ( $ENV{HOME} || $ENV{LOGDIR} || (getpwuid($>))[7] )}ex;</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch07-pgfId-480">Discussion</A></H3><PCLASS="para">The uses of tilde that we want to catch are:</P><PRECLASS="programlisting"> ~user ~user/blah ~ ~/blah</PRE><PCLASS="para">If no name follows the <CODECLASS="literal">~</CODE>, the current user's home directory is used.</P><PCLASS="para">This substitution uses <CODECLASS="literal">/e</CODE> to evaluate the replacement as Perl code. If a username follows the tilde, it's stored in <CODECLASS="literal">$1</CODE>, which <CODECLASS="literal">getpwnam</CODE> uses to extract the user's home directory out of the return list. This directory becomes the replacement string. If the tilde was not followed by a username, substitute in either the current <CODECLASS="literal">HOME</CODE> environment variable or the <CODECLASS="literal">LOGDIR</CODE> one. If neither of those environment variables is valid, look up the effective user ID's home directory.<ACLASS="indexterm"NAME="ch07-idx-1000009596-0"></A><ACLASS="indexterm"NAME="ch07-idx-1000009596-1"></A><ACLASS="indexterm"NAME="ch07-idx-1000009596-2"></A></P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch07-pgfId-1000008424">See Also</A></H3><PCLASS="para">Your system's <ICLASS="filename">getpwnam </I>(2) manpage; the <CODECLASS="literal">getpwnam</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>; <ACLASS="xref"HREF="ch09_07.htm"TITLE="Globbing, or Getting a List of Filenames Matching a Pattern">Recipe 9.6</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_03.htm"TITLE="7.2. 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