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<HTML><!--Distributed by F --><HEAD><TITLE>[Chapter 51] 51.3 ASCII Characters: Listing and Getting Values </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="1998-08-04T21:57:18Z"><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="ch51_01.htm"TITLE="51. Miscellaneous Useful Programs and Curiosities"><LINKREL="prev"HREF="ch51_02.htm"TITLE="51.2 How UNIX Keeps Time"><LINKREL="next"HREF="ch51_04.htm"TITLE="51.4 Who's On? "></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="ch51_02.htm"TITLE="51.2 How UNIX Keeps Time"><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 51.2 How UNIX Keeps Time"BORDER="0"></A></TD><TDALIGN="CENTER"VALIGN="TOP"WIDTH="171"><B><FONTFACE="ARIEL,HELVETICA,HELV,SANSERIF"SIZE="-1">Chapter 51<BR>Miscellaneous Useful Programs and Curiosities</FONT></B></TD><TDALIGN="RIGHT"VALIGN="TOP"WIDTH="172"><ACLASS="SECT1"HREF="ch51_04.htm"TITLE="51.4 Who's On? "><IMGSRC="gifs/txtnexta.gif"SRC="gifs/txtnexta.gif"ALT="Next: 51.4 Who's On? "BORDER="0"></A></TD></TR></TABLE> <HRALIGN="LEFT"WIDTH="515"TITLE="footer"></DIV><DIVCLASS="SECT1"><H2CLASS="sect1"><ACLASS="title"NAME="UPT-ART-4100">51.3 ASCII Characters: Listing and Getting Values </A></H2><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-59986"></A><ACLASS="indexterm"NAME="AUTOID-59989"></A><ACLASS="indexterm"NAME="AUTOID-59992"></A><ACLASS="indexterm"NAME="AUTOID-59994"></A><ACLASS="indexterm"NAME="AUTOID-59997"></A>Many UNIX systems come with a file named <EMCLASS="emphasis">ascii</EM>-in a directorynamed something like <EMCLASS="emphasis">/usr/pub</EM> or <EMCLASS="emphasis">/usr/share/lib/pub</EM>.It's a list of the ASCII character set with the octal and hexadecimalvalue of each character.Here are two lines from the octal section:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">|030 can|031 em |032 sub|033 esc|034 fs |035 gs |036 rs |037 us ||040 sp |041 ! |042 " |043 # |044 $ |045 % |046 & |047 ' |</PRE></BLOCKQUOTE></P><PCLASS="para">It's saying, for instance, that an escape (<CODECLASS="literal">esc</CODE>) character has avalue of 033 octal, and the percent sign (<CODECLASS="literal">%</CODE>) is 045 octal.</P><PCLASS="para">If your system doesn't have a file like that, you can type one in byhand in a few minutes; start with a printed ASCII chartor the <EMCLASS="emphasis">ascii</EM>(7) or <EMCLASS="emphasis">ascii</EM>(5) manual pages.You might also want to make your own version and replace names like<CODECLASS="literal">sub</CODE> with the key you'd type to get that character (in this case,the two-character representation <CODECLASS="literal">^Z</CODE>).If your UNIX system doesn't use ASCII, you can make a similar file for it.</P><PCLASS="para">Once you have that file, the following shell script, named <EMCLASS="emphasis">ascii</EM>, cansearch for the octal value of a character.For example:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">% <CODECLASS="userinput"><B>ascii esc</B></CODE>033% <CODECLASS="userinput"><B>ascii a</B></CODE>141% <CODECLASS="userinput"><B>ascii \&</B></CODE>046</PRE></BLOCKQUOTE></P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-60020"></A><ACLASS="indexterm"NAME="AUTOID-60023"></A>Remember to escape<SPANCLASS="link">special characters (<ACLASS="linkend"HREF="ch08_19.htm"TITLE='"Special" Characters and Operators '>8.19</A>)</SPAN>as I did with that ampersand (<CODECLASS="literal">&</CODE>).Here's the script:</P><PCLASS="para"><TABLECLASS="screen.co"BORDER="1"><TR><THVALIGN="TOP"><PRECLASS="calloutlist"> <ACLASS="co"HREF="ch44_06.htm"TITLE="44.6 Pattern Matching in case Statements ">case</A> <ACLASS="co"HREF="ch34_10.htm"TITLE="34.10 Referencing Portions of a Search String ">\(..\)..\1</A> </PRE></TH><TDVALIGN="TOP"><PRECLASS="screen"> #!/bin/shfile=/usr/pub/ascii# Make pattern with spaces to match field in $file exactly:<ACLASS="indexterm"NAME="AUTOID-60031"></A>case "$1" in[[\\/]) pat=" \\$1 " ;; # lets us search for [, \ and / ?) pat=" $1 " ;;??) pat="$1 " ;;???) pat="$1" ;;*) echo "Usage: `basename $0` char (char must be single character like 'a' or name like 'soh')." 1>&2 exit 1 ;;esacsed -n "1,/^\$/s/.*|\([0-9][0-9][0-9]\) $pat|.*/\1/p" $file</PRE></TD></TR></TABLE></P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-60037"></A>The script makes a<SPANCLASS="link"><EMCLASS="emphasis">sed</EM> (<ACLASS="linkend"HREF="ch34_24.htm"TITLE="Quick Reference: sed ">34.24</A>)</SPAN>expression that exactly matches an entry in the first section of the<EMCLASS="emphasis">ascii</EM> file (before the blank line that starts the hexadecimal section).For example, the command <CODECLASS="literal">ascii</CODE> <CODECLASS="literal">a</CODE> stores <EMCLASS="emphasis"><IMGSRC="../chars/squ.gif"ALT=" ">a<IMGSRC="../chars/squ.gif"ALT=" "></EM>in the <EMCLASS="emphasis">pat</EM> shell variable; the <EMCLASS="emphasis">sed</EM> substitute command becomes:</P><PCLASS="para"><BLOCKQUOTECLASS="screen"><PRECLASS="screen">s/|<CODECLASS="replaceable"><I>nnn</I></CODE><IMGSRC="../chars/squ.gif"ALT=" "><IMGSRC="../chars/squ.gif"ALT=" ">a<IMGSRC="../chars/squ.gif"ALT=" ">|/<CODECLASS="replaceable"><I>nnn</I></CODE>/p</PRE></BLOCKQUOTE></P><PCLASS="para">where <IMGSRC="../chars/squ.gif"ALT=" "> stands for a space and<CODECLASS="replaceable"><I>nnn</I></CODE> stands for the octal value of the entry for <CODECLASS="literal">a</CODE>.</P><PCLASS="para"><ACLASS="indexterm"NAME="AUTOID-60056"></A><ACLASS="indexterm"NAME="AUTOID-60059"></A>The<SPANCLASS="link"><EMCLASS="emphasis">jot</EM> (<ACLASS="linkend"HREF="ch45_11.htm"TITLE="The Multipurpose jot Command ">45.11</A>)</SPAN>command also translates a numeric value to the character it represents.But <EMCLASS="emphasis">jot</EM> doesn't show non-printable characters by name (like<CODECLASS="literal">esc</CODE>).</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="ch51_02.htm"TITLE="51.2 How UNIX Keeps Time"><IMGSRC="gifs/txtpreva.gif"SRC="gifs/txtpreva.gif"ALT="Previous: 51.2 How UNIX Keeps Time"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="ch51_04.htm"TITLE="51.4 Who's On? 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