403 lines
5.8 KiB
HTML
403 lines
5.8 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML
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><HEAD
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><TITLE
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>Introduction</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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REL="HOME"
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TITLE="Bash Guide for Beginners"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="The GNU sed stream editor"
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HREF="chap_05.html"><LINK
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REL="PREVIOUS"
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TITLE="The GNU sed stream editor"
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HREF="chap_05.html"><LINK
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REL="NEXT"
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TITLE="Interactive editing"
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HREF="sect_05_02.html"></HEAD
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><BODY
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CLASS="sect1"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#840084"
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ALINK="#0000FF"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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SUMMARY="Header navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Bash Guide for Beginners</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="chap_05.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 5. The GNU sed stream editor</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="sect_05_02.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="sect1"
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><H1
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CLASS="sect1"
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><A
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NAME="sect_05_01"
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></A
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>5.1. Introduction</H1
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><DIV
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CLASS="sect2"
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><H2
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CLASS="sect2"
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><A
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NAME="sect_05_01_01"
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></A
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>5.1.1. What is sed?</H2
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><P
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>A <SPAN
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CLASS="application"
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>Stream EDitor</SPAN
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> is used to perform basic transformations on text read from a file or a pipe. The result is sent to standard output. The syntax for the <B
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CLASS="command"
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>sed</B
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> command has no output file specification, but results can be saved to a file using output redirection. The editor does not modify the original input.</P
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><P
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>What distinguishes <B
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CLASS="command"
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>sed</B
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> from other editors, such as <B
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CLASS="command"
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>vi</B
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> and <B
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CLASS="command"
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>ed</B
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>, is its ability to filter text that it gets from a pipeline feed. You do not need to interact with the editor while it is running; that is why <B
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CLASS="command"
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>sed</B
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> is sometimes called a <EM
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>batch editor</EM
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>. This feature allows use of editing commands in scripts, greatly easing repetitive editing tasks. When facing replacement of text in a large number of files, <B
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CLASS="command"
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>sed</B
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> is a great help.</P
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></DIV
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><DIV
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CLASS="sect2"
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><H2
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CLASS="sect2"
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><A
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NAME="sect_05_01_02"
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></A
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>5.1.2. sed commands</H2
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><P
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>The <B
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CLASS="command"
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>sed</B
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> program can perform text pattern substitutions and deletions using regular expressions, like the ones used with the <B
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CLASS="command"
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>grep</B
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> command; see <A
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HREF="sect_04_02.html"
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>Section 4.2</A
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>.</P
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><P
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>The editing commands are similar to the ones used in the <B
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CLASS="command"
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>vi</B
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> editor:</P
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><DIV
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CLASS="table"
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><A
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NAME="tab_05_01"
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></A
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><P
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><B
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>Table 5-1. Sed editing commands</B
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></P
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><TABLE
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BORDER="1"
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CLASS="CALSTABLE"
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><THEAD
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><TR
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><TH
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Command</TH
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><TH
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Result</TH
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></TR
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></THEAD
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><TBODY
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>a\</TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Append text below current line.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>c\</TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Change text in the current line with new text.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>d</TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Delete text.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>i\</TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Insert text above current line.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>p</TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Print text.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>r</TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Read a file.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>s</TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Search and replace text.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>w</TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Write to a file.</TD
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></TR
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></TBODY
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></TABLE
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></DIV
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><P
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>Apart from editing commands, you can give options to <B
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CLASS="command"
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>sed</B
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>. An overview is in the table below:</P
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><DIV
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CLASS="table"
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><A
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NAME="tab_05_02"
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></A
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><P
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><B
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>Table 5-2. Sed options</B
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></P
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><TABLE
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BORDER="1"
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CLASS="CALSTABLE"
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><THEAD
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><TR
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><TH
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Option</TH
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><TH
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Effect</TH
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></TR
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></THEAD
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><TBODY
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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><TT
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CLASS="option"
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>-e SCRIPT</TT
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></TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Add the commands in SCRIPT to the set of commands to be run while processing the input.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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><TT
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CLASS="option"
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>-f</TT
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></TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Add the commands contained in the file SCRIPT-FILE to the set of commands to be run while processing the input.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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><TT
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CLASS="option"
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>-n</TT
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></TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Silent mode.</TD
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></TR
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><TR
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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><TT
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CLASS="option"
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>-V</TT
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></TD
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><TD
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ALIGN="LEFT"
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VALIGN="MIDDLE"
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>Print version information and exit.</TD
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></TR
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></TBODY
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></TABLE
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></DIV
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><P
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>The <B
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CLASS="command"
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>sed</B
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> info pages contain more information; we only list the most frequently used commands and options here.</P
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></DIV
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></DIV
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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SUMMARY="Footer navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="chap_05.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="index.html"
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ACCESSKEY="H"
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>Home</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><A
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HREF="sect_05_02.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>The GNU sed stream editor</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="chap_05.html"
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ACCESSKEY="U"
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>Up</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>Interactive editing</TD
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></TR
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></TABLE
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></DIV
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></BODY
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> |