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<HTML><HEAD><TITLE>Recipe 8.2. Counting Lines (or Paragraphs or Records) in a File (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="1999-07-02T01:38:25Z"><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="ch08_01.htm"TITLE="8. File Contents"><LINKREL="prev"HREF="ch08_02.htm"TITLE="8.1. Reading Lines with Continuation Characters"><LINKREL="next"HREF="ch08_04.htm"TITLE="8.3. Processing Every Word in a File"></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="ch08_02.htm"TITLE="8.1. Reading Lines with Continuation Characters"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 8.1. Reading Lines with Continuation Characters"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1"><ACLASS="chapter"REL="up"HREF="ch08_01.htm"TITLE="8. File Contents"></A></FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch08_04.htm"TITLE="8.3. Processing Every Word in a File"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 8.3. Processing Every Word in a File"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch08-chap08_counting_0">8.2. Counting Lines (or Paragraphs or Records) in a File</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch08-pgfId-248">Problem<ACLASS="indexterm"NAME="ch08-idx-1000004622-0"></A><ACLASS="indexterm"NAME="ch08-idx-1000004622-1"></A><ACLASS="indexterm"NAME="ch08-idx-1000004622-2"></A><ACLASS="indexterm"NAME="ch08-idx-1000004622-3"></A><ACLASS="indexterm"NAME="ch08-idx-1000004622-4"></A></A></H3><PCLASS="para">You need to compute the number of lines in a file.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch08-pgfId-254">Solution</A></H3><PCLASS="para">Many systems have a <EMCLASS="emphasis">wc</EM><ACLASS="indexterm"NAME="ch08-idx-1000004628-0"></A> program to count lines in a file:</P><PRECLASS="programlisting">$count = `wc -l < $file`;die "wc failed: $?" if $?;chomp($count);</PRE><PCLASS="para">You could also open the file and read line-by-line until the end, counting lines as you go:</P><PRECLASS="programlisting">open(FILE, "< $file") or die "can't open $file: $!";$count++ while <FILE>;# $count now holds the number of lines read</PRE><PCLASS="para">Here's the fastest solution, assuming your line terminator really <EMCLASS="emphasis">is</EM> <CODECLASS="literal">"\n"</CODE>:</P><PRECLASS="programlisting">$count += tr/\n/\n/ while sysread(FILE, $_, 2 ** 16);</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch08-pgfId-278">Discussion</A></H3><PCLASS="para">Although you can use <CODECLASS="literal">-s</CODE> <CODECLASS="literal">$file</CODE> to determine the file size in bytes, you generally cannot use it to derive a line count. See the Introduction to <ACLASS="xref"HREF="ch09_01.htm"TITLE="Directories">Chapter 9, <CITECLASS="chapter">Directories</CITE></A>, for more on <CODECLASS="literal">-s</CODE>.</P><PCLASS="para">If you can't or don't want to call another program to do your dirty work, you can emulate <EMCLASS="emphasis">wc</EM> by opening up and reading the file yourself:</P><PRECLASS="programlisting">open(FILE, "< $file") or die "can't open $file: $!";$count++ while <FILE>;# $count now holds the number of lines read</PRE><PCLASS="para">Another way of writing this is:</P><PRECLASS="programlisting">open(FILE, "< $file") or die "can't open $file: $!";for ($count=0; <FILE>; $count++) { }</PRE><PCLASS="para">If you're not reading from any other files, you don't need the <CODECLASS="literal">$count</CODE> variable in this case. The special variable <CODECLASS="literal">$.</CODE> holds the number of lines read since a filehandle was last explicitly <CODECLASS="literal">close</CODE>d:</P><PRECLASS="programlisting">1 while <FILE>;$count = $.;</PRE><PCLASS="para">This reads all the records in the file and discards them.</P><PCLASS="para">To count paragraphs, set the global input record separator variable <CODECLASS="literal">$/</CODE> to the empty string (<CODECLASS="literal">""</CODE>) before reading to make <> read a paragraph at a time.</P><PRECLASS="programlisting">$/ = ''; # enable paragraph mode for all readsopen(FILE, $file) or die "can't open $file: $!";1 while <FILE>;$para_count = $.;<ACLASS="indexterm"NAME="ch08-idx-1000004624-0"></A><ACLASS="indexterm"NAME="ch08-idx-1000004624-1"></A><ACLASS="indexterm"NAME="ch08-idx-1000004624-2"></A><ACLASS="indexterm"NAME="ch08-idx-1000004624-3"></A><ACLASS="indexterm"NAME="ch08-idx-1000004624-4"></A></PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch08-pgfId-314">See Also</A></H3><PCLASS="para">Your system's <ICLASS="filename">wc</I> (1) manpage; the <CODECLASS="literal">$/</CODE> entry in <ICLASS="filename">perlvar </I>(1), and in the <ACLASS="olink"HREF="../prog/ch02_09.htm">"Special Variables"</A> section of <ACLASS="olink"HREF="../prog/ch02_01.htm">Chapter 2</A> of <ACLASS="citetitle"HREF="../prog/index.htm"TITLE="Programming Perl"><CITECLASS="citetitle">Programming Perl</CITE></A>; the Introduction to <ACLASS="xref"HREF="ch09_01.htm"TITLE="Directories">Chapter 9</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="ch08_02.htm"TITLE="8.1. Reading Lines with Continuation Characters"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 8.1. Reading Lines with Continuation Characters"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="ch08_04.htm"TITLE="8.3. Processing Every Word in a File"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 8.3. Processing Every Word in a File"BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="228">8.1. Reading Lines with Continuation Characters</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">8.3. 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