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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 25] 25.10 Squash Extra Blank Lines </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="1998-08-04T21:43:21Z"><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="ch25_01.htm"TITLE="25. Showing What's in a File"><LINKREL="prev"HREF="ch25_09.htm"TITLE="25.9 Adding and Deleting White Space "><LINKREL="next"HREF="ch25_11.htm"TITLE="25.11 crush: A cat that Skips all Blank Lines "></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="ch25_09.htm"TITLE="25.9 Adding and Deleting White Space "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 25.9 Adding and Deleting White Space "BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 25<BR>Showing What's in a File</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch25_11.htm"TITLE="25.11 crush: A cat that Skips all Blank Lines "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 25.11 crush: A cat that Skips all Blank Lines "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-7909">25.10 Squash Extra Blank Lines </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-27782"></A><ACLASS="indexterm"NAME="AUTOID-27784"></A>Reading output with lots of empty lines can be a waste of screen space.For instance, some System V versions of<SPANCLASS="link"><EMCLASS="emphasis">man</EM> (<ACLASS="linkend"HREF="ch50_01.htm#UPT-ART-4910"TITLE="UNIX Online Documentation ">50.1</A>)</SPAN>show all the blank lines between manual pages.To stop that, read your file or pipe it through <EMCLASS="emphasis">cat -s</EM>.(Many versions of<SPANCLASS="link"><EMCLASS="emphasis">more</EM> (<ACLASS="linkend"HREF="ch25_03.htm"TITLE="Using more to Page Through Files ">25.3</A>)</SPAN>have a similar <EMCLASS="emphasis">-s</EM> option.)The <EMCLASS="emphasis">-s</EM> option replaces multiple blank lines with a single blank line.(If your <EMCLASS="emphasis">cat</EM> doesn't have <EMCLASS="emphasis">-s</EM>, see the <EMCLASS="emphasis">sed</EM> alternativeat the end.)</P><PCLASS="para"><EMCLASS="emphasis">cat -s</EM> might not always seem to work.The problem is usually that the "empty" lines haveSPACE, TAB, or CTRL-mcharacters on them.The fix is to let <EMCLASS="emphasis">sed</EM> "erase" lines with those invisible characterson them:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>sed 's/^[<KBDCLASS="keycap">[SPACE]</KBD><KBDCLASS="keycap">[TAB]</KBD><KBDCLASS="keycap">[CTRL-v]</KBD><KBDCLASS="keycap">[CTRL-m]</KBD>]*$//' </B></CODE><CODECLASS="replaceable"><I>file</I></CODE><CODECLASS="userinput"><B> | cat -s</B></CODE></PRE></BLOCKQUOTE></P><PCLASS="para">In<SPANCLASS="link"><EMCLASS="emphasis">vi</EM> (<ACLASS="linkend"HREF="ch31_06.htm"TITLE="Protecting Keys from Interpretation by ex ">31.6</A>)</SPAN>and many<SPANCLASS="link">terminal drivers (<ACLASS="linkend"HREF="ch42_01.htm#UPT-ART-1142"TITLE="Making Sense Out of the Terminal Mess ">42.1</A>)</SPAN>,the CTRL-v character quotes the CTRL-m (RETURN)so that character doesn't end the current line.</P><PCLASS="para"> If you don't have <EMCLASS="emphasis">cat -s</EM>, then <EMCLASS="emphasis">sed</EM> can do both jobs:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>sed -e 's/^[<KBDCLASS="keycap">[SPACE]</KBD><KBDCLASS="keycap">[TAB]</KBD><KBDCLASS="keycap">[CTRL-v]</KBD><KBDCLASS="keycap">[CTRL-m]</KBD>]*$//' -e '/./,/^$/!d' </B></CODE><CODECLASS="replaceable"><I>file</I></CODE></PRE></BLOCKQUOTE></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="ch25_09.htm"TITLE="25.9 Adding and Deleting White Space "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 25.9 Adding and Deleting White Space "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="ch25_11.htm"TITLE="25.11 crush: A cat that Skips all Blank Lines "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 25.11 crush: A cat that Skips all Blank Lines "BORDER="0"></A></TD></TR><TR><TDALIGN="LEFT"VALIGN="TOP"WIDTH="172">25.9 Adding and Deleting White Space 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