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<HTML><HEAD><TITLE>Recipe 15.11. Editing Input (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="1999-07-02T01:43:23Z"><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_11.htm"TITLE="15.10. Reading Passwords"><LINKREL="next"HREF="ch15_13.htm"TITLE="15.12. Managing the Screen"></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_11.htm"TITLE="15.10. Reading Passwords"><IMGSRC="../gifs/txtpreva.gif"ALT="Previous: 15.10. Reading Passwords"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_13.htm"TITLE="15.12. Managing the Screen"><IMGSRC="../gifs/txtnexta.gif"ALT="Next: 15.12. Managing the Screen"BORDER="0"></A></TD></TR></TABLE></DIV><DIVCLASS="sect1"><H2CLASS="sect1"><ACLASS="title"NAME="ch15-22445">15.11. Editing Input</A></H2><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch15-pgfId-1007">Problem<ACLASS="indexterm"NAME="ch15-idx-1000005126-0"></A><ACLASS="indexterm"NAME="ch15-idx-1000005126-1"></A><ACLASS="indexterm"NAME="ch15-idx-1000005126-2"></A><ACLASS="indexterm"NAME="ch15-idx-1000005126-3"></A><ACLASS="indexterm"NAME="ch15-idx-1000005126-4"></A><ACLASS="indexterm"NAME="ch15-idx-1000005126-5"></A></A></H3><PCLASS="para">You want a user to be able to edit a line before sending it to you for reading.</P></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch15-pgfId-1013">Solution</A></H3><PCLASS="para">Use the standard Term::ReadLine library along with the Term::ReadLine::Gnu module from CPAN:</P><PRECLASS="programlisting">use Term::ReadLine;$term = Term::ReadLine->new("APP DESCRIPTION");$OUT = $term->OUT || *STDOUT;$term->addhistory($fake_line);$line = $term->readline(PROMPT);print $OUT "Any program output\n";</PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch15-pgfId-1037">Discussion</A></H3><PCLASS="para">The program in <ACLASS="xref"HREF="ch15_12.htm#ch15-15537"TITLE="vbsh">Example 15.4</A> acts as a crude shell. It reads a line and passes it to the shell to execute. The <CODECLASS="literal">readline</CODE> method reads a line from the terminal, with editing and history recall. It automatically adds the user's line to the history.</P><DIVCLASS="example"><H4CLASS="example"><ACLASS="title"NAME="ch15-15537">Example 15.4: vbsh</A></H4><PRECLASS="programlisting">#!/usr/bin/perl -w# <ACLASS="indexterm"NAME="ch15-idx-1000005004-0"></A>vbsh - very bad shelluse strict;use Term::ReadLine;use POSIX qw(:sys_wait_h);my $term = Term::ReadLine->new("Simple Shell");my $OUT = $term->OUT() || *STDOUT;my $cmd;while (defined ($cmd = $term->readline('$ ') )) { my @output = `$cmd`; my $exit_value = $? >> 8; my $signal_num = $? & 127; my $dumped_core = $? & 128; printf $OUT "Program terminated with status %d from signal %d%s\n", $exit_value, $signal_num, $dumped_core ? " (core dumped)" : ""; print @output; $term->addhistory($cmd);}</PRE></DIV><PCLASS="para">If you want to seed the history with your own functions, use the <CODECLASS="literal">addhistory</CODE> method:</P><PRECLASS="programlisting">$term->addhistory($seed_line);</PRE><PCLASS="para">You can't seed with more than one line at a time. To remove a line from the history, use the <CODECLASS="literal">remove_history</CODE> method, which takes an index into the history list. <CODECLASS="literal">0</CODE> is the first (least recent) entry, <CODECLASS="literal">1</CODE> the second, and so on up to the most recent history lines.</P><PRECLASS="programlisting">$term->remove_history($line_number);</PRE><PCLASS="para">To get a list of history lines, use the <CODECLASS="literal">GetHistory</CODE> method, which returns a list of the lines: <ACLASS="indexterm"NAME="ch15-idx-1000006232-0"></A></P><PRECLASS="programlisting">@history = $term->GetHistory;<ACLASS="indexterm"NAME="ch15-idx-1000005128-0"></A><ACLASS="indexterm"NAME="ch15-idx-1000005128-1"></A><ACLASS="indexterm"NAME="ch15-idx-1000005128-2"></A><ACLASS="indexterm"NAME="ch15-idx-1000005128-3"></A><ACLASS="indexterm"NAME="ch15-idx-1000005128-4"></A><ACLASS="indexterm"NAME="ch15-idx-1000005128-5"></A></PRE></DIV><DIVCLASS="sect2"><H3CLASS="sect2"><ACLASS="title"NAME="ch15-pgfId-1097">See Also</A></H3><PCLASS="para">The documentation for the standard Term::ReadLine module and the Term::ReadLine::Gnu from CPAN</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_11.htm"TITLE="15.10. 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