sedawk.html

Shall高级编程

ALIGN="LEFT"
VALIGN="TOP"
>Delete all blank lines.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>1,/^$/d</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Delete from beginning of input up to, and including
	        first blank line.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>/Jones/p</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Print only lines containing <SPAN
CLASS="QUOTE"
>"Jones"</SPAN
> (with
	        <SPAN
CLASS="TOKEN"
>-n</SPAN
> option).</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>s/Windows/Linux/</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Substitute <SPAN
CLASS="QUOTE"
>"Linux"</SPAN
> for first instance
	        of <SPAN
CLASS="QUOTE"
>"Windows"</SPAN
> found in each input line.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>s/BSOD/stability/g</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Substitute <SPAN
CLASS="QUOTE"
>"stability"</SPAN
> for every instance
	        of <SPAN
CLASS="QUOTE"
>"BSOD"</SPAN
> found in each input line.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>s/ *$//</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Delete all spaces at the end of every line.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>s/00*/0/g</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Compress all consecutive sequences of zeroes into
	        a single zero.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>/GUI/d</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Delete all lines containing <SPAN
CLASS="QUOTE"
>"GUI"</SPAN
>.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="OPTION"
>s/GUI//g</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Delete all instances of <SPAN
CLASS="QUOTE"
>"GUI"</SPAN
>, leaving the 
	        remainder of each line intact.</TD
></TR
></TBODY
></TABLE
><HR></DIV
><P
>Substituting a zero-length string for another is equivalent
       to deleting that string within a line of input. This leaves the
       remainder of the line intact. Applying <TT
CLASS="USERINPUT"
><B
>s/GUI//</B
></TT
>   
       to the line
       <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="USERINPUT"
><B
>The most important parts of any application are its GUI and sound effects</B
></TT
></PRE
></TD
></TR
></TABLE
>
       results in
       <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
> <TT
CLASS="COMPUTEROUTPUT"
>The most important parts of any application are its  and sound effects</TT
></PRE
></TD
></TR
></TABLE
></P
><P
>A backslash forces the <B
CLASS="COMMAND"
>sed</B
> replacement
       command to continue on to the next line. This has the effect of
       using the <I
CLASS="FIRSTTERM"
>newline</I
> at the end of the first
       line as the <I
CLASS="FIRSTTERM"
>replacement string</I
>.

       <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;s/^  */\
   2&nbsp;/g</PRE
></TD
></TR
></TABLE
>

       This substitution replaces line-beginning spaces with a
       newline. The net result is to replace paragraph indents with a
       blank line between paragraphs.</P
><P
>An address range followed by one or more operations may require
       open and closed curly brackets, with appropriate newlines. 
       <TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>   1&nbsp;/[0-9A-Za-z]/,/^$/{
   2&nbsp;/^$/d
   3&nbsp;}</PRE
></TD
></TR
></TABLE
>
       This deletes only the first of each set of consecutive blank
       lines. That might be useful for single-spacing a text file,
       but retaining the blank line(s) between paragraphs.</P
><DIV
CLASS="NOTE"
><TABLE
CLASS="NOTE"
WIDTH="100%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="common/note.png"
HSPACE="5"
ALT="Note"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>The usual delimiter that <I
CLASS="FIRSTTERM"
>sed</I
> uses is
      <SPAN
CLASS="TOKEN"
>/</SPAN
>. However, <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>sed</I
></SPAN
> allows other
      delimiters, such as <SPAN
CLASS="TOKEN"
>%</SPAN
>. This is useful when
      <SPAN
CLASS="TOKEN"
>/</SPAN
> is part of a replacement string, as in a file pathname.
      See <A
HREF="loops.html#FINDSTRING"
>Example 10-9</A
> and <A
HREF="filearchiv.html#STRIPC"
>Example 15-31</A
>.</P
></TD
></TR
></TABLE
></DIV
><P
><A
NAME="DOUBLESPACE"
></A
></P
><DIV
CLASS="TIP"
><TABLE
CLASS="TIP"
WIDTH="100%"
BORDER="0"
><TR
><TD
WIDTH="25"
ALIGN="CENTER"
VALIGN="TOP"
><IMG
SRC="common/tip.png"
HSPACE="5"
ALT="Tip"></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><P
>A quick way to double-space a text file is <TT
CLASS="USERINPUT"
><B
>sed G
       filename</B
></TT
>.</P
></TD
></TR
></TABLE
></DIV
><P
>For illustrative examples of sed within shell scripts, see:
       <OL
TYPE="1"
><LI
><P
><A
HREF="wrapper.html#EX3"
>Example 33-1</A
></P
></LI
><LI
><P
><A
HREF="wrapper.html#EX4"
>Example 33-2</A
></P
></LI
><LI
><P
><A
HREF="moreadv.html#EX57"
>Example 15-3</A
></P
></LI
><LI
><P
><A
HREF="contributed-scripts.html#RN"
>Example A-2</A
></P
></LI
><LI
><P
><A
HREF="textproc.html#GRP"
>Example 15-17</A
></P
></LI
><LI
><P
><A
HREF="textproc.html#COL"
>Example 15-26</A
></P
></LI
><LI
><P
><A
HREF="contributed-scripts.html#BEHEAD"
>Example A-12</A
></P
></LI
><LI
><P
><A
HREF="contributed-scripts.html#TREE"
>Example A-17</A
></P
></LI
><LI
><P
><A
HREF="contributed-scripts.html#TREE2"
>Example A-18</A
></P
></LI
><LI
><P
><A
HREF="filearchiv.html#STRIPC"
>Example 15-31</A
></P
></LI
><LI
><P
><A
HREF="loops.html#FINDSTRING"
>Example 10-9</A
></P
></LI
><LI
><P
><A
HREF="mathc.html#BASE"
>Example 15-46</A
></P
></LI
><LI
><P
><A
HREF="contributed-scripts.html#MAILFORMAT"
>Example A-1</A
></P
></LI
><LI
><P
><A
HREF="textproc.html#RND"
>Example 15-14</A
></P
></LI
><LI
><P
><A
HREF="textproc.html#WF"
>Example 15-12</A
></P
></LI
><LI
><P
><A
HREF="contributed-scripts.html#LIFESLOW"
>Example A-10</A
></P
></LI
><LI
><P
><A
HREF="here-docs.html#SELFDOCUMENT"
>Example 18-12</A
></P
></LI
><LI
><P
><A
HREF="textproc.html#DICTLOOKUP"
>Example 15-18</A
></P
></LI
><LI
><P
><A
HREF="contributed-scripts.html#WHX"
>Example A-31</A
></P
></LI
><LI
><P
><A
HREF="contributed-scripts.html#TOHTML"
>Example A-26</A
></P
></LI
></OL
>
     </P
><P
>For a more extensive treatment of <I
CLASS="FIRSTTERM"
>sed</I
>,
        check the appropriate references in the <A
HREF="biblio.html"
><I
>Bibliography</I
></A
>.</P
></DIV
></DIV
><H3
CLASS="FOOTNOTES"
>Notes</H3
><TABLE
BORDER="0"
CLASS="FOOTNOTES"
WIDTH="100%"
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN21071"
HREF="sedawk.html#AEN21071"
>[1]</A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
>Sed executes without user
          intervention.</P
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="5%"
><A
NAME="FTN.AEN21077"
HREF="sedawk.html#AEN21077"
>[2]</A
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
WIDTH="95%"
><P
>If no address range is specified, the default
	  is <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>all</I
></SPAN
> lines.</P
></TD
></TR
></TABLE
><DIV
CLASS="NAVFOOTER"
><HR
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WIDTH="100%"><TABLE
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HREF="refcards.html"
ACCESSKEY="P"
>Prev</A
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