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<HTML><HEAD><TITLE>Recipe 15.10. Reading Passwords (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="1999-07-02T01:43:22Z"><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="ch15_01.htm"TITLE="15. User Interfaces"><LINKREL="prev"HREF="ch15_10.htm"TITLE="15.9. Checking for Waiting Input"><LINKREL="next"HREF="ch15_12.htm"TITLE="15.11. Editing Input"></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="ch15_10.htm"TITLE="15.9. Checking for Waiting Input"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 15.9. Checking for Waiting Input"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="228"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1"><ACLASS="chapter"REL="up"HREF="ch15_01.htm"TITLE="15. User Interfaces"></A></FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="228"><ACLASS="sect1"HREF="ch15_12.htm"TITLE="15.11. Editing Input"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 15.11. Editing Input"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch15-42438">15.10. Reading Passwords</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch15-pgfId-931">Problem<ACLASS="indexterm"NAME="ch15-idx-1000005120-0"></A><ACLASS="indexterm"NAME="ch15-idx-1000005120-1"></A><ACLASS="indexterm"NAME="ch15-idx-1000005120-2"></A><ACLASS="indexterm"NAME="ch15-idx-1000005120-3"></A><ACLASS="indexterm"NAME="ch15-idx-1000005120-4"></A><ACLASS="indexterm"NAME="ch15-idx-1000005120-5"></A><ACLASS="indexterm"NAME="ch15-idx-1000005120-6"></A></A></H3><PCLASS="para">You want to read input from the keyboard without the keystrokes being echoed on the screen. For instance, you want to read passwords as <EMCLASS="emphasis">passwd</EM> does, i.e. without displaying the user's password.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch15-pgfId-937">Solution</A></H3><PCLASS="para">Use the CPAN module Term::ReadKey, set the input mode to <CODECLASS="literal">noecho</CODE>, and then use <CODECLASS="literal">ReadLine</CODE>:</P><PRECLASS="programlisting">use Term::ReadKey;ReadMode('noecho');$password = ReadLine(0);</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch15-pgfId-951">Discussion</A></H3><PCLASS="para"><ACLASS="xref"HREF="ch15_11.htm#ch15-37288"TITLE="checkuser">Example 15.3</A> shows how to verify a user's password. If your system uses shadow passwords, only the superuser can get the encrypted form of the password with <CODECLASS="literal">getpwuid</CODE>. Everyone else just gets <CODECLASS="literal">*</CODE> as the password field of the database, which is useless for verifying passwords.</P><DIVCLASS="example"><H4CLASS="example"><ACLASS="title"NAME="ch15-37288">Example 15.3: checkuser</A></H4><PRECLASS="programlisting">#!/usr/bin/perl -w# <ACLASS="indexterm"NAME="ch15-idx-1000005001-0"></A>checkuser - demonstrates reading and checking a user's passworduse Term::ReadKey;print "Enter your password: ";ReadMode 'noecho';$password = ReadLine 0;chomp $password;ReadMode 'normal';print "\n";($username, $encrypted) = ( getpwuid $< )[0,1];if (crypt($password, $encrypted) ne $encrypted) { die "You are not $username\n";} else { print "Welcome, $username\n";}<ACLASS="indexterm"NAME="ch15-idx-1000005122-0"></A><ACLASS="indexterm"NAME="ch15-idx-1000005122-1"></A><ACLASS="indexterm"NAME="ch15-idx-1000005122-2"></A><ACLASS="indexterm"NAME="ch15-idx-1000005122-3"></A><ACLASS="indexterm"NAME="ch15-idx-1000005122-4"></A><ACLASS="indexterm"NAME="ch15-idx-1000005122-5"></A><ACLASS="indexterm"NAME="ch15-idx-1000005122-6"></A></PRE></DIV></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch15-pgfId-997">See Also</A></H3><PCLASS="para">The documentation for the Term::ReadKey module from CPAN; the <ACLASS="olink"HREF="../prog/ch03_022.htm"><CODECLASS="literal">crypt</CODE></A> and <ACLASS="olink"HREF="../prog/ch03_063.htm"><CODECLASS="literal">getpwuid</CODE></A> functions in <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> and in <ICLASS="filename">perlfunc </I>(1), which demonstrate using the <ICLASS="filename">stty</I> (1) command; your system's <ICLASS="filename">crypt </I>(3) and <ICLASS="filename">passwd </I>(5) manpages (if you have them)</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="ch15_10.htm"TITLE="15.9. 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