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<HTML><HEAD><TITLE>Recipe 1.14. Trimming Blanks from the Ends of a String (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="1999-07-02T01:29:20Z"><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="ch01_01.htm"TITLE="1. Strings"><LINKREL="prev"HREF="ch01_14.htm"TITLE="1.13. Escaping Characters"><LINKREL="next"HREF="ch01_16.htm"TITLE="1.15. Parsing Comma-Separated Data"></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="ch01_14.htm"TITLE="1.13. Escaping Characters"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 1.13. Escaping Characters"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1"><ACLASS="chapter"REL="up"HREF="ch01_01.htm"TITLE="1. Strings"></A></FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch01_16.htm"TITLE="1.15. Parsing Comma-Separated Data"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 1.15. Parsing Comma-Separated Data"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch01-34997">1.14. Trimming Blanks from the Ends of a String</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch01-pgfId-1589">Problem <ACLASS="indexterm"NAME="ch01-idx-1000010329-0"></A><ACLASS="indexterm"NAME="ch01-idx-1000010329-1"></A><ACLASS="indexterm"NAME="ch01-idx-1000010329-2"></A><ACLASS="indexterm"NAME="ch01-idx-1000010329-3"></A><ACLASS="indexterm"NAME="ch01-idx-1000010329-4"></A><ACLASS="indexterm"NAME="ch01-idx-1000010329-5"></A></A></H3><PCLASS="para">You have read a string that may have leading or trailing whitespace, and you want to remove it.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch01-pgfId-1595">Solution</A></H3><PCLASS="para">Use a pair of pattern substitutions to get rid of them:</P><PRECLASS="programlisting">$string =~ s/^\s+//;$string =~ s/\s+$//;</PRE><PCLASS="para">You can also write a function that returns the new value:</P><PRECLASS="programlisting">$string = trim($string);@many = trim(@many);sub trim { my @out = @_; for (@out) { s/^\s+//; s/\s+$//; } return wantarray ? @out : $out[0];}</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch01-pgfId-1629">Discussion</A></H3><PCLASS="para">This problem has various solutions, but this is the most efficient for the common case.</P><PCLASS="para">If you want to remove the last character from the string, use the <CODECLASS="literal">chop</CODE> function. Version 5 added <CODECLASS="literal">chomp</CODE>, which removes the last character if and only if it is contained in the <CODECLASS="literal">$/</CODE> variable, "<CODECLASS="literal">\n</CODE>" by default. These are often used to remove the trailing newline from input:</P><PRECLASS="programlisting"># print what's typed, but surrounded by >< symbolswhile(<STDIN>) { chomp; print ">$_<\n";}</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch01-pgfId-1647">See Also</A></H3><PCLASS="para">The <CODECLASS="literal">s///</CODE> operator in <EMCLASS="emphasis">perlre </EM>(1) and <ICLASS="filename">perlop </I>(1) and the <ACLASS="olink"HREF="../prog/ch02_04.htm">"Pattern Matching"</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 <CODECLASS="literal">chomp</CODE> and <CODECLASS="literal">chop</CODE> functions in <EMCLASS="emphasis">perlfunc</EM> (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>; we trim leading and trailing whitespace in the <CODECLASS="literal">getnum</CODE> function in <ACLASS="xref"HREF="ch02_02.htm"TITLE="Checking Whether a String Is a Valid Number">Recipe 2.1</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="ch01_14.htm"TITLE="1.13. 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