ch45_11.htm

the unix power tools

CLASS="para"
>If you want the output separated by a string other than a newline,
use the <EM
CLASS="emphasis"
>-s</EM
> option.
For example, to have the output of the
previous command separated by spaces, enter:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>jot -s &quot; &quot; - 1 -3 -2</B
></CODE
>
1 -1 -3</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>That's <EM
CLASS="emphasis"
>jot</EM
> in its no-frills form, already potentially useful for
any writer of shell scripts.
However, <EM
CLASS="emphasis"
>jot</EM
> does quite
a lot more.
The <EM
CLASS="emphasis"
>-c</EM
> option can be used to show
<SPAN
CLASS="link"
>ASCII (<A
CLASS="linkend"
HREF="ch51_03.htm"
TITLE="ASCII Characters: Listing and Getting Values "
>51.3</A
>)</SPAN
>
characters instead of
integers.
To print out the character for ASCII 65 (decimal), for example, try:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>jot -c 1 65</B
></CODE
>
A</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-52960"
></A
><A
CLASS="indexterm"
NAME="AUTOID-52963"
></A
>You can also do the ASCII-to-decimal conversion in reverse, by just
specifying a character in place of the lower bound:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>jot 1 A</B
></CODE
>
65</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>This can be handy if you want an automatic listing of all 26 letters:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>jot -c 26 A</B
></CODE
>
A
B
C
   ...</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-52973"
></A
><A
CLASS="indexterm"
NAME="AUTOID-52976"
></A
><A
CLASS="indexterm"
NAME="AUTOID-52979"
></A
><A
CLASS="indexterm"
NAME="AUTOID-52982"
></A
><A
CLASS="indexterm"
NAME="AUTOID-52985"
></A
>The <EM
CLASS="emphasis"
>-r</EM
> option produces random numbers, which is very useful in
shells with no random number generator (such as the Bourne or C
shells).  To create a 6-digit random number, try:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>jot -r 1 100000 999999</B
></CODE
>
523467</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>&#13;(Using <EM
CLASS="emphasis"
>-r</EM
>, the fourth numerical argument, if specified, is
taken to be a seed for the random number.)</P
><P
CLASS="para"
>The <EM
CLASS="emphasis"
>-b</EM
> option can be used to repeat 
a given word, much like the
<SPAN
CLASS="link"
><EM
CLASS="emphasis"
>yes</EM
> (<A
CLASS="linkend"
HREF="ch23_04.htm"
TITLE='Answer "Yes&quot; or "No&quot; Forever with yes'
>23.4</A
>)</SPAN
>
command:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>jot -b lunchtime! 3</B
></CODE
>
lunchtime!
lunchtime!
lunchtime!</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-53002"
></A
><A
CLASS="indexterm"
NAME="AUTOID-53005"
></A
><A
CLASS="indexterm"
NAME="AUTOID-53008"
></A
>The <EM
CLASS="emphasis"
>jot</EM
> manual page suggests a clever way of using this feature:
if you want to search for lines in files that have 40 or more
characters, you could do this using regular expressions, but you'd
have to count out all those dots.</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>grep &quot;........................................&quot; <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>Using <EM
CLASS="emphasis"
>jot</EM
>, you can pat yourself on the back for being
ingenious (or for just reading the manpage!):</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>grep `jot -s &quot;&quot; -b . 40` <CODE
CLASS="replaceable"
><I
>file</I
></CODE
></PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-53021"
></A
>But the most powerful feature of <EM
CLASS="emphasis"
>jot</EM
> comes with its <EM
CLASS="emphasis"
>-w</EM
>
option.
The <EM
CLASS="emphasis"
>-w</EM
> option accepts a word containing format
conversion characters as used by the <EM
CLASS="emphasis"
>printf(&nbsp;)</EM
> function.
(For example, <CODE
CLASS="literal"
>%d</CODE
> prints a decimal argument; <CODE
CLASS="literal"
>%h</CODE
> prints
hexadecimal.)
If you aren't familiar with the <EM
CLASS="emphasis"
>printf(&nbsp;)</EM
> format conversions,
read your <EM
CLASS="emphasis"
>printf</EM
>(3) manual page or check any C programming book.</P
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-53032"
></A
><A
CLASS="indexterm"
NAME="AUTOID-53033"
></A
>This allows you to combine strings with <EM
CLASS="emphasis"
>jot</EM
> output, a useful
feature for manipulating temporary files within scripts. 
For example, suppose you have a shell script that creates multiple
temporary files that you want to remove at the end of the script.
You might have even created the files using <EM
CLASS="emphasis"
>jot</EM
> earlier in the
script, as shown previously:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>for counter in `jot 10 1`
do
   <CODE
CLASS="replaceable"
><I
>whatever commands</I
></CODE
> &gt; tmp$counter
done</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>Then later on you want to remove the files.
You could do
another loop, but it's more efficient to just enter:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>rm `jot -w tmp%d 10 1`</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>The <EM
CLASS="emphasis"
>jot</EM
> command expands to the strings <EM
CLASS="emphasis"
>tmp1</EM
> through
<EM
CLASS="emphasis"
>tmp10</EM
>, which are the names of the temporary files created
earlier in the script.<A
CLASS="indexterm"
NAME="AUTOID-53048"
></A
><A
CLASS="indexterm"
NAME="AUTOID-53049"
></A
></P
><DIV
CLASS="sect1info"
><P
CLASS="SECT1INFO"
>- <SPAN
CLASS="authorinitials"
>LM</SPAN
></P
></DIV
></DIV
><DIV
CLASS="htmlnav"
><P
></P
><HR
ALIGN="LEFT"
WIDTH="515"
TITLE="footer"><TABLE
WIDTH="515"
BORDER="0"
CELLSPACING="0"
CELLPADDING="0"
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="172"
><A
CLASS="SECT1"
HREF="ch45_10.htm"
TITLE="45.10 Removing a File Once It's Opened&nbsp;- for Security and Easy Cleanup"
><IMG
SRC="gifs/txtpreva.gif"
SRC="gifs/txtpreva.gif"
ALT="Previous: 45.10 Removing a File Once It's Opened&nbsp;- for Security and Easy Cleanup"
BORDER="0"></A
></TD
><TD
ALIGN="CENTER"
VALIGN="TOP"
WIDTH="171"
><A
CLASS="book"
HREF="index.htm"
TITLE="UNIX Power Tools"
><IMG
SRC="gifs/txthome.gif"
SRC="gifs/txthome.gif"
ALT="UNIX Power Tools"
BORDER="0"></A
></TD
><TD
ALIGN="RIGHT"
VALIGN="TOP"
WIDTH="172"
><A
CLASS="SECT1"
HREF="ch45_12.htm"
TITLE="45.12 Parameter Substitution "
><IMG
SRC="gifs/txtnexta.gif"
SRC="gifs/txtnexta.gif"
ALT="Next: 45.12 Parameter Substitution "
BORDER="0"></A
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="172"
>45.10 Removing a File Once It's Opened&nbsp;- for Security and Easy Cleanup</TD
><TD
ALIGN="CENTER"
VALIGN="TOP"
WIDTH="171"
><A
CLASS="index"
HREF="index/idx_0.htm"
TITLE="Book Index"
><IMG
SRC="gifs/index.gif"
SRC="gifs/index.gif"
ALT="Book Index"
BORDER="0"></A
></TD
><TD
ALIGN="RIGHT"
VALIGN="TOP"
WIDTH="172"
>45.12 Parameter Substitution </TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="515"
TITLE="footer"><IMG
SRC="gifs/smnavbar.gif"
SRC="gifs/smnavbar.gif"
USEMAP="#map"
BORDER="0"
ALT="The UNIX CD Bookshelf Navigation"><MAP
NAME="map"
><AREA
SHAPE="RECT"
COORDS="0,0,73,21"
HREF="../index.htm"
ALT="The UNIX CD Bookshelf"><AREA
SHAPE="RECT"
COORDS="74,0,163,21"
HREF="index.htm"
ALT="UNIX Power Tools"><AREA
SHAPE="RECT"
COORDS="164,0,257,21"
HREF="../unixnut/index.htm"
ALT="UNIX in a Nutshell"><AREA
SHAPE="RECT"
COORDS="258,0,321,21"
HREF="../vi/index.htm"
ALT="Learning the vi Editor"><AREA
SHAPE="RECT"
COORDS="322,0,378,21"
HREF="../sedawk/index.htm"
ALT="sed &amp; awk"><AREA
SHAPE="RECT"
COORDS="379,0,438,21"
HREF="../ksh/index.htm"
ALT="Learning the Korn Shell"><AREA
SHAPE="RECT"
COORDS="439,0,514,21"
HREF="../lrnunix/index.htm"
ALT="Learning the UNIX Operating System"></MAP
></DIV
></BODY
></HTML
>