ch09_24.htm

the unix power tools

></P
><P
CLASS="para"
>This works with most any UNIX command&nbsp;- not just <EM
CLASS="emphasis"
>rcp</EM
>.
For example, if I want to print the files, I can use:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>lpr `cat /tmp/bk$$`</B
></CODE
></PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
></P
></LI
><LI
CLASS="listitem"
><P
CLASS="para"
>If I'll be doing a lot of work with the filenames, typing the backquotes
over and over is a pain.
I'll store the filenames in a
<SPAN
CLASS="link"
>shell variable (<A
CLASS="linkend"
HREF="ch06_08.htm"
TITLE="Shell Variables "
>6.8</A
>)</SPAN
>:</P
><UL
CLASS="itemizedlist"
><LI
CLASS="listitem"
><P
CLASS="para"
>First, pick a name for the shell variable.
I usually choose <EM
CLASS="emphasis"
>temp</EM
> because it's not used on my account.
You should check the name you choose before you set it by typing <CODE
CLASS="literal"
>echo</CODE
>
<CODE
CLASS="literal"
>&quot;$</CODE
><CODE
CLASS="replaceable"
><I
>varname</I
></CODE
><CODE
CLASS="literal"
>&quot;</CODE
>; be sure it's empty or useless.</P
></LI
><LI
CLASS="listitem"
><P
CLASS="para"
>Store the filenames from your temporary file:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>set temp=(`cat /tmp/bk$$`)</B
></CODE
> <I
CLASS="lineannotation"
>...C shells</I
> 
$ <CODE
CLASS="userinput"
><B
>temp=&quot;`cat /tmp/bk$$`&quot;</B
></CODE
> <I
CLASS="lineannotation"
>...Bourne shells</I
></PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
></P
></LI
><LI
CLASS="listitem"
><P
CLASS="para"
>Use the shell variable.
For example:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>cp $temp</B
></CODE
><CODE
CLASS="replaceable"
><I
> backupdir</I
></CODE
>
% <CODE
CLASS="userinput"
><B
>vi $temp</B
></CODE
>
% ...</PRE
></BLOCKQUOTE
></P
></LI
></UL
></LI
></OL
><P
CLASS="para"
>(Sometimes,
<SPAN
CLASS="link"
><EM
CLASS="emphasis"
>find</EM
> with operators like <EM
CLASS="emphasis"
>-newer</EM
> (<A
CLASS="linkend"
HREF="ch17_08.htm"
TITLE="Exact File Time Comparisons "
>17.8</A
>)</SPAN
>
is easier&nbsp;- but <EM
CLASS="emphasis"
>find</EM
> searches subdirectories too,
unless you use
<SPAN
CLASS="link"
><EM
CLASS="emphasis"
>-prune</EM
> (<A
CLASS="linkend"
HREF="ch17_23.htm"
TITLE="Finding Files with -prune "
>17.23</A
>)</SPAN
>.)
Oh, try to remember to <EM
CLASS="emphasis"
>rm</EM
> the temp file when you're 
done with it.</P
></DIV
><DIV
CLASS="sect2"
><H3
CLASS="sect2"
><A
CLASS="title"
NAME="UPT-ART-7630-SECT-1.2"
>9.24.2 Search for Text with grep </A
></H3
><P
CLASS="para"
><A
CLASS="indexterm"
NAME="AUTOID-11385"
></A
><A
CLASS="indexterm"
NAME="AUTOID-11388"
></A
>The <EM
CLASS="emphasis"
>grep</EM
>
<SPAN
CLASS="link"
><EM
CLASS="emphasis"
>-l</EM
> option (<A
CLASS="linkend"
HREF="ch15_07.htm"
TITLE="Getting a List of Matching Files with grep -l "
>15.7</A
>)</SPAN
>
gives you a list of filenames that match a string&nbsp;- that might be all I
need.
But sometimes I need to see the lines that <EM
CLASS="emphasis"
>grep</EM
> found to decide
whether to include that file or not.
Here's how:</P
><OL
CLASS="orderedlist"
><LI
CLASS="listitem"
><P
CLASS="para"
>Search the files.
Be sure that your <EM
CLASS="emphasis"
>grep</EM
>-like command will print the filename before
each matching line:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>% <CODE
CLASS="userinput"
><B
>egrep -i &quot;summar(y|ies)&quot; * &gt; /tmp/bk$$</B
></CODE
></PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
></P
></LI
><LI
CLASS="listitem"
><P
CLASS="para"
>Edit the temporary file.
The lines will look something like this:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>a0066:Here is a summary of the different components:
a0183:Summary: String functions in awk
a0183:for a summary of all the string functions
a0184:Let's start wlth a short summary how awk treats command
a1000:Here's a summary of the rules that UNIX uses to interpret paths:
a1000:Here's a summary of the different sorts of wildcards available:
a1680:cumulative summary files and ASCII reports in 
a2710:In summary, \fIcomm\fP is similar to \fIdiff\fP:
   ...</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>Leave a line for each file that you want to operate on; delete the rest:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>a0066:Here is a summary of the different components:
a0183:Summary: String functions in awk
a1000:Here's a summary of the different sorts of wildcards available:
   ...</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
></P
></LI
><LI
CLASS="listitem"
><P
CLASS="para"
>Strip off everything after the filenames.
Unless any of your filenames have colons (<CODE
CLASS="literal"
>:</CODE
>) in them, you
can tell <EM
CLASS="emphasis"
>vi</EM
> to strip off the colons and everything after them.
That command is:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
><CODE
CLASS="userinput"
><B
>:%s/:.*//</B
></CODE
></PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>If there's a chance that a filename might be repeated (because
<EM
CLASS="emphasis"
>grep</EM
> matched more than one line), filter the filenames through
<EM
CLASS="emphasis"
>sort -u</EM
> to get rid of duplicates.
In <EM
CLASS="emphasis"
>vi</EM
>, type:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
><CODE
CLASS="userinput"
><B
>:%!sort -u</B
></CODE
></PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>Like before, what's left is a list of filenames:</P
><P
CLASS="para"
><BLOCKQUOTE
CLASS="screen"
><PRE
CLASS="screen"
>a0066
a0183
a1000
    ...</PRE
></BLOCKQUOTE
></P
><P
CLASS="para"
>&#13;You can feed them to whatever command you need to run, as in the
previous example.</P
></LI
></OL
><P
CLASS="para"
>I hope those two examples give you the idea, which is: learn what UNIX utilities
are &quot;out there&quot;-and how to grab and edit their output to do what you want.</P
></DIV
><DIV
CLASS="sect1info"
><P
CLASS="SECT1INFO"
>- <SPAN
CLASS="authorinitials"
>JP</SPAN
></P
></DIV
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