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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 23] 23.4 Answer "Yes" or "No" Forever with yes</TITLE><METANAME="DC.title"CONTENT="UNIX Power Tools"><METANAME="DC.creator"CONTENT="Jerry Peek, Tim O'Reilly & Mike Loukides"><METANAME="DC.publisher"CONTENT="O'Reilly & Associates, Inc."><METANAME="DC.date"CONTENT="1998-08-04T21:40:59Z"><METANAME="DC.type"CONTENT="Text.Monograph"><METANAME="DC.format"CONTENT="text/html"SCHEME="MIME"><METANAME="DC.source"CONTENT="1-56592-260-3"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="ch23_01.htm"TITLE="23. Removing Files"><LINKREL="prev"HREF="ch23_03.htm"TITLE="23.3 Tricks for Making rm Safer "><LINKREL="next"HREF="ch23_05.htm"TITLE="23.5 Remove Some, Leave Some "></HEAD><BODYBGCOLOR="#FFFFFF"TEXT="#000000"><DIVCLASS="htmlnav"><H1><IMGSRC="gifs/smbanner.gif"ALT="UNIX Power Tools"USEMAP="#srchmap"BORDER="0"></H1><MAPNAME="srchmap"><AREASHAPE="RECT"COORDS="0,0,466,58"HREF="index.htm"ALT="UNIX Power Tools"><AREASHAPE="RECT"COORDS="467,0,514,18"HREF="jobjects/fsearch.htm"ALT="Search this book"></MAP><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch23_03.htm"TITLE="23.3 Tricks for Making rm Safer "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 23.3 Tricks for Making rm Safer "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 23<BR>Removing Files</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch23_05.htm"TITLE="23.5 Remove Some, Leave Some "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 23.5 Remove Some, Leave Some "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-0361">23.4 Answer "Yes" or "No" Forever with yes</A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-25256"></A><ACLASS="indexterm"NAME="AUTOID-25259"></A>Some commands - like <EMCLASS="emphasis">rm -i</EM>, <EMCLASS="emphasis">find -ok</EM>, and so on - ask users toanswer a "do it or not?" question from the keyboard.For example, you might use a file-deleting program named <EMCLASS="emphasis">del</EM> thatasks before deleting each file:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>del *</B></CODE>Remove file1? <CODECLASS="userinput"><B>y</B></CODE>Remove file2? <CODECLASS="userinput"><B>y</B></CODE> ...</PRE></BLOCKQUOTE></P><PCLASS="para">If you answer <CODECLASS="literal">y</CODE>, then the file will be deleted.</P><PCLASS="para">What if you want to run a command that's going to ask you 200 questionsand you want to answer <CODECLASS="literal">y</CODE> to all of them, but you don't want to typeall those <CODECLASS="literal">y</CODE>'s in from the keyboard?Pipe the output of <CODECLASS="literal">yes</CODE> to the command; it will answer <CODECLASS="literal">y</CODE> for you:<ACLASS="indexterm"NAME="AUTOID-25277"></A></P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>yes | del *</B></CODE>Remove file1?Remove file2? ...</PRE></BLOCKQUOTE></P><PCLASS="para">If you want to answer <CODECLASS="literal">n</CODE> to all the questions, you can do:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>yes n | del *</B></CODE></PRE></BLOCKQUOTE></P><BLOCKQUOTECLASS="note"><PCLASS="para"><STRONG>NOTE:</STRONG> Not all UNIX commands read their standard input for answers to prompts.If a command opens your terminal(<SPANCLASS="link"><EMCLASS="emphasis">/dev/tty</EM> (<ACLASS="linkend"HREF="ch45_20.htm"TITLE="Overview: Open Files and File Descriptors ">45.20</A>)</SPAN>)directly to read youranswer, <CODECLASS="literal">yes</CODE> won't work.Try<SPANCLASS="link"><EMCLASS="emphasis">expect</EM> (<ACLASS="linkend"HREF="ch09_26.htm"TITLE="Expect ">9.26</A>)</SPAN>instead.</P></BLOCKQUOTE><TABLECLASS="para.programreference"BORDER="1"><TR><THVALIGN="TOP"><ACLASS="programreference"HREF="examples/index.htm"TITLE="yes">yes</A><BR></TH><TDVALIGN="TOP"> <EMCLASS="emphasis">yes</EM> knows how to say more than just <EMCLASS="emphasis">y</EM> or <EMCLASS="emphasis">n</EM>.Article<ACLASS="xref"HREF="ch42_07.htm"TITLE="termtest: Send Repeated Characters to Terminal ">42.7</A>shows how to test a terminal with <EMCLASS="emphasis">yes</EM>.</TD></TR></TABLE><PCLASS="para">The CD-ROM has GNU's <EMCLASS="emphasis">yes</EM>.<ACLASS="indexterm"NAME="AUTOID-25303"></A><ACLASS="indexterm"NAME="AUTOID-25304"></A></P><DIVCLASS="sect1info"><PCLASS="SECT1INFO">- <SPANCLASS="authorinitials">JP</SPAN></P></DIV></DIV><DIVCLASS="htmlnav"><P></P><HRALIGN="LEFT"WIDTH="515"TITLE="footer"><TABLEWIDTH="515"BORDER="0"CELLSPACING="0"CELLPADDING="0"><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch23_03.htm"TITLE="23.3 Tricks for Making rm Safer "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 23.3 Tricks for Making rm Safer "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><ACLASS="book"HREF="index.htm"TITLE="UNIX Power Tools"><IMGSRC="gifs/txthome.gif"SRC="gifs/txthome.gif"ALT="UNIX Power Tools"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch23_05.htm"TITLE="23.5 Remove Some, Leave Some "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 23.5 Remove Some, Leave Some "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">23.3 Tricks for Making rm Safer </TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><ACLASS="index"HREF="index/idx_0.htm"TITLE="Book Index"><IMGSRC="gifs/index.gif"SRC="gifs/index.gif"ALT="Book Index"BORDER="0"></A></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172">23.5 Remove Some, Leave Some </TD></TR></TABLE><HRALIGN="LEFT"WIDTH="515"TITLE="footer"><IMGSRC="gifs/smnavbar.gif"SRC="gifs/smnavbar.gif"USEMAP="#map"BORDER="0"ALT="The UNIX CD Bookshelf Navigation"><MAPNAME="map"><AREASHAPE="RECT"COORDS="0,0,73,21"HREF="../index.htm"ALT="The UNIX CD Bookshelf"><AREASHAPE="RECT"COORDS="74,0,163,21"HREF="index.htm"ALT="UNIX Power Tools"><AREASHAPE="RECT"COORDS="164,0,257,21"HREF="../unixnut/index.htm"ALT="UNIX in a Nutshell"><AREASHAPE="RECT"COORDS="258,0,321,21"HREF="../vi/index.htm"ALT="Learning the vi Editor"><AREASHAPE="RECT"COORDS="322,0,378,21"HREF="../sedawk/index.htm"ALT="sed & awk"><AREASHAPE="RECT"COORDS="379,0,438,21"HREF="../ksh/index.htm"ALT="Learning the Korn Shell"><AREASHAPE="RECT"COORDS="439,0,514,21"HREF="../lrnunix/index.htm"ALT="Learning the UNIX Operating System"></MAP></DIV></BODY></HTML>⌨️ 快捷键说明
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