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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 25] 25.11 crush: A cat that Skips all 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="1998-08-04T21:43:23Z"><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_10.htm"TITLE="25.10 Squash Extra Blank Lines "><LINKREL="next"HREF="ch25_12.htm"TITLE="25.12 Double Space, Triple Space ... "></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_10.htm"TITLE="25.10 Squash Extra Blank Lines "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 25.10 Squash Extra Blank Lines "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_12.htm"TITLE="25.12 Double Space, Triple Space ... "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 25.12 Double Space, Triple Space ... "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-4250">25.11 crush: A cat that Skips all Blank Lines </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-27829"></A><ACLASS="indexterm"NAME="AUTOID-27831"></A>Sometimes I have a series of files, or just one file, with lots of blank lines.Some systems have a <EMCLASS="emphasis">-s</EM> option to <EMCLASS="emphasis">cat</EM> that causes it to compressadjacent blank lines into one.If that option isn't available, youcan use <EMCLASS="emphasis">crush</EM>.The <EMCLASS="emphasis">crush</EM> script skips all lines that are empty or have onlyblanks and/or TABs.Here it is:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen"> #!/bin/sed -f/^[ ]*$/d</PRE></BLOCKQUOTE></P><PCLASS="para">The brackets, <CODECLASS="literal">[ ]</CODE>, have a TAB and a space in them.That file doesn't even use a shell, so it's efficient; the kernel<SPANCLASS="link">starts <EMCLASS="emphasis">sed</EM> directly (<ACLASS="linkend"HREF="ch45_03.htm"TITLE="Don't Need a Shell for Your Script? Don't Use One ">45.3</A>)</SPAN>and gives it the script itself as the input file expected with the<EMCLASS="emphasis">-f</EM> option.If your UNIX can't execute files directly with <CODECLASS="literal">#!</CODE>, type in this versioninstead:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">exec sed '/^[ ]*$/d' ${1+"$@"}</PRE></BLOCKQUOTE></P><PCLASS="para">It starts a shell, then<SPANCLASS="link"><EMCLASS="emphasis">exec</EM> replaces the shell with <EMCLASS="emphasis">sed</EM> (<ACLASS="linkend"HREF="ch45_07.htm"TITLE="The exec Command ">45.7</A>)</SPAN>.The <CODECLASS="literal">${1+"$@"}</CODE> works around a<SPANCLASS="link">problem with argument handling (<ACLASS="linkend"HREF="ch46_07.htm"TITLE="Quoting and Command-Line Parameters ">46.7</A>)</SPAN>in some Bourne shells.</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_10.htm"TITLE="25.10 Squash Extra Blank Lines "><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 25.10 Squash Extra Blank Lines "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_12.htm"TITLE="25.12 Double Space, Triple Space ... 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