1774 lines
26 KiB
HTML
1774 lines
26 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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>Basic Commands</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="Advanced Bash-Scripting Guide"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="External Filters, Programs and Commands"
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HREF="external.html"><LINK
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REL="PREVIOUS"
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TITLE="External Filters, Programs and Commands"
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HREF="external.html"><LINK
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REL="NEXT"
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TITLE="Complex Commands"
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HREF="moreadv.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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>Advanced Bash-Scripting Guide: </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="external.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 16. External Filters, Programs and Commands</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="moreadv.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="BASIC"
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></A
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>16.1. Basic Commands</H1
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><P
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></P
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><DIV
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CLASS="VARIABLELIST"
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><P
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><B
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><A
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NAME="BASICCOMMANDS1"
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></A
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>The first commands a novice learns</B
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></P
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><DL
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><DT
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><A
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NAME="LSREF"
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></A
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><B
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CLASS="COMMAND"
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>ls</B
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></DT
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><DD
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><P
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>The basic file <SPAN
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CLASS="QUOTE"
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>"list"</SPAN
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> command. It is all too easy
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to underestimate the power of this humble command. For
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example, using the <TT
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CLASS="OPTION"
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>-R</TT
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>, recursive option,
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<B
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CLASS="COMMAND"
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>ls</B
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> provides a tree-like listing of
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a directory structure. Other useful options are
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<TT
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CLASS="OPTION"
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>-S</TT
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>, sort listing by file size,
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<TT
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CLASS="OPTION"
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>-t</TT
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>, sort by file modification time,
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<TT
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CLASS="OPTION"
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>-v</TT
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>, sort by (numerical) version numbers
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embedded in the filenames,
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<A
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NAME="AEN10025"
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HREF="#FTN.AEN10025"
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><SPAN
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CLASS="footnote"
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>[1]</SPAN
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></A
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>
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<TT
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CLASS="OPTION"
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>-b</TT
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>, show escape characters, and
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<TT
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CLASS="OPTION"
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>-i</TT
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>, show file inodes (see <A
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HREF="moreadv.html#IDELETE"
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>Example 16-4</A
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>).</P
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><P
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> <TABLE
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BORDER="1"
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BGCOLOR="#E0E0E0"
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WIDTH="90%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
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><PRE
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CLASS="SCREEN"
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><TT
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CLASS="PROMPT"
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>bash$ </TT
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><TT
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CLASS="USERINPUT"
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><B
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>ls -l</B
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></TT
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>
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<TT
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CLASS="COMPUTEROUTPUT"
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>-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter10.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter11.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter12.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter1.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter2.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter3.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:49 Chapter_headings.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:49 Preface.txt</TT
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>
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<TT
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CLASS="PROMPT"
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>bash$ </TT
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><TT
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CLASS="USERINPUT"
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><B
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>ls -lv</B
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></TT
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>
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<TT
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CLASS="COMPUTEROUTPUT"
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> total 0
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:49 Chapter_headings.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:49 Preface.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter1.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter2.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter3.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter10.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter11.txt
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-rw-rw-r-- 1 bozo bozo 0 Sep 14 18:44 chapter12.txt</TT
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></PRE
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></FONT
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></TD
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></TR
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></TABLE
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></P
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><DIV
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CLASS="TIP"
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><P
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></P
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><TABLE
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CLASS="TIP"
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WIDTH="90%"
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BORDER="0"
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><TR
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><TD
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WIDTH="25"
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ALIGN="CENTER"
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VALIGN="TOP"
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><IMG
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SRC="../images/tip.gif"
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HSPACE="5"
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ALT="Tip"></TD
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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><P
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> The <I
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CLASS="FIRSTTERM"
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>ls</I
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> command returns a
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non-zero <A
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HREF="exit-status.html#EXITSTATUSREF"
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>exit status</A
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> when
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attempting to list a non-existent file.
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<TABLE
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BORDER="1"
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BGCOLOR="#E0E0E0"
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WIDTH="90%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
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><PRE
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CLASS="SCREEN"
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><TT
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CLASS="PROMPT"
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>bash$ </TT
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><TT
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CLASS="USERINPUT"
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><B
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>ls abc</B
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></TT
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>
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<TT
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CLASS="COMPUTEROUTPUT"
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>ls: abc: No such file or directory</TT
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>
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<TT
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CLASS="PROMPT"
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>bash$ </TT
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><TT
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CLASS="USERINPUT"
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><B
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>echo $?</B
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></TT
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>
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<TT
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CLASS="COMPUTEROUTPUT"
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>2</TT
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></PRE
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></FONT
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></TD
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></TR
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></TABLE
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>
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</P
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></TD
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></TR
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></TABLE
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></DIV
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><DIV
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CLASS="EXAMPLE"
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><A
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NAME="EX40"
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></A
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><P
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><B
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>Example 16-1. Using <I
|
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CLASS="FIRSTTERM"
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>ls</I
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> to create a table of contents
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for burning a <SPAN
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CLASS="ABBREV"
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>CDR</SPAN
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> disk</B
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></P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="90%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
|
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><PRE
|
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CLASS="PROGRAMLISTING"
|
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>#!/bin/bash
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# ex40.sh (burn-cd.sh)
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# Script to automate burning a CDR.
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SPEED=10 # May use higher speed if your hardware supports it.
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IMAGEFILE=cdimage.iso
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CONTENTSFILE=contents
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# DEVICE=/dev/cdrom For older versions of cdrecord
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DEVICE="1,0,0"
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DEFAULTDIR=/opt # This is the directory containing the data to be burned.
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# Make sure it exists.
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# Exercise: Add a test for this.
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# Uses Joerg Schilling's "cdrecord" package:
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# http://www.fokus.fhg.de/usr/schilling/cdrecord.html
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|
|
# If this script invoked as an ordinary user, may need to suid cdrecord
|
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#+ chmod u+s /usr/bin/cdrecord, as root.
|
|
# Of course, this creates a security hole, though a relatively minor one.
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|
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if [ -z "$1" ]
|
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then
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IMAGE_DIRECTORY=$DEFAULTDIR
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# Default directory, if not specified on command-line.
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else
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IMAGE_DIRECTORY=$1
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fi
|
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# Create a "table of contents" file.
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ls -lRF $IMAGE_DIRECTORY > $IMAGE_DIRECTORY/$CONTENTSFILE
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# The "l" option gives a "long" file listing.
|
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# The "R" option makes the listing recursive.
|
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# The "F" option marks the file types (directories get a trailing /).
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echo "Creating table of contents."
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|
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# Create an image file preparatory to burning it onto the CDR.
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mkisofs -r -o $IMAGEFILE $IMAGE_DIRECTORY
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echo "Creating ISO9660 file system image ($IMAGEFILE)."
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# Burn the CDR.
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echo "Burning the disk."
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echo "Please be patient, this will take a while."
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wodim -v -isosize dev=$DEVICE $IMAGEFILE
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# In newer Linux distros, the "wodim" utility assumes the
|
|
#+ functionality of "cdrecord."
|
|
exitcode=$?
|
|
echo "Exit code = $exitcode"
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|
exit $exitcode</PRE
|
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></FONT
|
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></TD
|
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></TR
|
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></TABLE
|
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></DIV
|
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></DD
|
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><DT
|
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><A
|
|
NAME="CATREF"
|
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></A
|
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><B
|
|
CLASS="COMMAND"
|
|
>cat</B
|
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>, <B
|
|
CLASS="COMMAND"
|
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>tac</B
|
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></DT
|
|
><DD
|
|
><P
|
|
><B
|
|
CLASS="COMMAND"
|
|
>cat</B
|
|
>, an acronym for
|
|
<I
|
|
CLASS="WORDASWORD"
|
|
>concatenate</I
|
|
>,
|
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lists a file to <TT
|
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CLASS="FILENAME"
|
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>stdout</TT
|
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>. When
|
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combined with redirection (<SPAN
|
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CLASS="TOKEN"
|
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>></SPAN
|
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> or
|
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<SPAN
|
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CLASS="TOKEN"
|
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>>></SPAN
|
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>), it is commonly used to concatenate
|
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files.
|
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<A
|
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NAME="CATUSES"
|
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></A
|
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>
|
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="90%"
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><TR
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><TD
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><FONT
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COLOR="#000000"
|
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><PRE
|
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CLASS="PROGRAMLISTING"
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># Uses of 'cat'
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cat filename # Lists the file.
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cat file.1 file.2 file.3 > file.123 # Combines three files into one.</PRE
|
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></FONT
|
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></TD
|
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></TR
|
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></TABLE
|
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>
|
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The <TT
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CLASS="OPTION"
|
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>-n</TT
|
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> option to <B
|
|
CLASS="COMMAND"
|
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>cat</B
|
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>
|
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inserts consecutive numbers before all lines of the
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target file(s). The <TT
|
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CLASS="OPTION"
|
|
>-b</TT
|
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> option numbers
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only the non-blank lines. The <TT
|
|
CLASS="OPTION"
|
|
>-v</TT
|
|
> option
|
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echoes nonprintable characters, using <SPAN
|
|
CLASS="TOKEN"
|
|
>^</SPAN
|
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>
|
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notation. The <TT
|
|
CLASS="OPTION"
|
|
>-s</TT
|
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> option squeezes multiple
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consecutive blank lines into a single blank line.</P
|
|
><P
|
|
>See also <A
|
|
HREF="textproc.html#LNUM"
|
|
>Example 16-28</A
|
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> and <A
|
|
HREF="textproc.html#ROT13"
|
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>Example 16-24</A
|
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>.</P
|
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><DIV
|
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CLASS="NOTE"
|
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><P
|
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></P
|
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><TABLE
|
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CLASS="NOTE"
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WIDTH="90%"
|
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BORDER="0"
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><TR
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><TD
|
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WIDTH="25"
|
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ALIGN="CENTER"
|
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VALIGN="TOP"
|
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><IMG
|
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SRC="../images/note.gif"
|
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HSPACE="5"
|
|
ALT="Note"></TD
|
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><TD
|
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ALIGN="LEFT"
|
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VALIGN="TOP"
|
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><P
|
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><A
|
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NAME="CATLESSEFF"
|
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></A
|
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>
|
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In a <A
|
|
HREF="special-chars.html#PIPEREF"
|
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>pipe</A
|
|
>, it may be
|
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more efficient to <A
|
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HREF="io-redirection.html#IOREDIRREF"
|
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>redirect</A
|
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>
|
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the <TT
|
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CLASS="FILENAME"
|
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>stdin</TT
|
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> to a file, rather than to
|
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<B
|
|
CLASS="COMMAND"
|
|
>cat</B
|
|
> the file.
|
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</P
|
|
><P
|
|
> <TABLE
|
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BORDER="0"
|
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BGCOLOR="#E0E0E0"
|
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WIDTH="90%"
|
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><TR
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><TD
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><FONT
|
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COLOR="#000000"
|
|
><PRE
|
|
CLASS="PROGRAMLISTING"
|
|
>cat filename | tr a-z A-Z
|
|
|
|
tr a-z A-Z < filename # Same effect, but starts one less process,
|
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#+ and also dispenses with the pipe.</PRE
|
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></FONT
|
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></TD
|
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></TR
|
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></TABLE
|
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>
|
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</P
|
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></TD
|
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></TR
|
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></TABLE
|
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></DIV
|
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><P
|
|
><B
|
|
CLASS="COMMAND"
|
|
>tac</B
|
|
>, is the inverse of
|
|
<I
|
|
CLASS="WORDASWORD"
|
|
>cat</I
|
|
>, listing a file backwards from its end.</P
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="REVREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>rev</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
>reverses each line of a file, and outputs to
|
|
<TT
|
|
CLASS="FILENAME"
|
|
>stdout</TT
|
|
>. This does not have the same effect
|
|
as <B
|
|
CLASS="COMMAND"
|
|
>tac</B
|
|
>, as it preserves the order of
|
|
the lines, but flips each one around (mirror image).</P
|
|
><P
|
|
> <TABLE
|
|
BORDER="1"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
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><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="SCREEN"
|
|
><TT
|
|
CLASS="PROMPT"
|
|
>bash$ </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>cat file1.txt</B
|
|
></TT
|
|
>
|
|
<TT
|
|
CLASS="COMPUTEROUTPUT"
|
|
>This is line 1.
|
|
This is line 2.</TT
|
|
>
|
|
|
|
|
|
<TT
|
|
CLASS="PROMPT"
|
|
>bash$ </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>tac file1.txt</B
|
|
></TT
|
|
>
|
|
<TT
|
|
CLASS="COMPUTEROUTPUT"
|
|
>This is line 2.
|
|
This is line 1.</TT
|
|
>
|
|
|
|
|
|
<TT
|
|
CLASS="PROMPT"
|
|
>bash$ </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>rev file1.txt</B
|
|
></TT
|
|
>
|
|
<TT
|
|
CLASS="COMPUTEROUTPUT"
|
|
>.1 enil si sihT
|
|
.2 enil si sihT</TT
|
|
>
|
|
</PRE
|
|
></FONT
|
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></TD
|
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></TR
|
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></TABLE
|
|
>
|
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</P
|
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></DD
|
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><DT
|
|
><A
|
|
NAME="CPREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>cp</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
>This is the file copy command. <TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>cp file1
|
|
file2</B
|
|
></TT
|
|
> copies <TT
|
|
CLASS="FILENAME"
|
|
>file1</TT
|
|
>
|
|
to <TT
|
|
CLASS="FILENAME"
|
|
>file2</TT
|
|
>, overwriting
|
|
<TT
|
|
CLASS="FILENAME"
|
|
>file2</TT
|
|
> if it already exists (see <A
|
|
HREF="moreadv.html#EX42"
|
|
>Example 16-6</A
|
|
>).</P
|
|
><DIV
|
|
CLASS="TIP"
|
|
><P
|
|
></P
|
|
><TABLE
|
|
CLASS="TIP"
|
|
WIDTH="90%"
|
|
BORDER="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="25"
|
|
ALIGN="CENTER"
|
|
VALIGN="TOP"
|
|
><IMG
|
|
SRC="../images/tip.gif"
|
|
HSPACE="5"
|
|
ALT="Tip"></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><P
|
|
>Particularly useful are the <TT
|
|
CLASS="OPTION"
|
|
>-a</TT
|
|
>
|
|
archive flag (for copying an entire directory tree),
|
|
the <TT
|
|
CLASS="OPTION"
|
|
>-u</TT
|
|
> update flag (which prevents
|
|
overwriting identically-named newer files), and the
|
|
<TT
|
|
CLASS="OPTION"
|
|
>-r</TT
|
|
> and <TT
|
|
CLASS="OPTION"
|
|
>-R</TT
|
|
> recursive
|
|
flags.</P
|
|
><P
|
|
><TABLE
|
|
BORDER="0"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="PROGRAMLISTING"
|
|
>cp -u source_dir/* dest_dir
|
|
# "Synchronize" dest_dir to source_dir
|
|
#+ by copying over all newer and not previously existing files.</PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></P
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="MVREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>mv</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
>This is the file <I
|
|
CLASS="FIRSTTERM"
|
|
>move</I
|
|
> command.
|
|
It is equivalent to a combination of <B
|
|
CLASS="COMMAND"
|
|
>cp</B
|
|
>
|
|
and <B
|
|
CLASS="COMMAND"
|
|
>rm</B
|
|
>. It may be used to move multiple
|
|
files to a directory, or even to rename a directory. For
|
|
some examples of using <B
|
|
CLASS="COMMAND"
|
|
>mv</B
|
|
> in a script,
|
|
see <A
|
|
HREF="parameter-substitution.html#RFE"
|
|
>Example 10-11</A
|
|
> and <A
|
|
HREF="contributed-scripts.html#RN"
|
|
>Example A-2</A
|
|
>.</P
|
|
><DIV
|
|
CLASS="NOTE"
|
|
><P
|
|
></P
|
|
><TABLE
|
|
CLASS="NOTE"
|
|
WIDTH="90%"
|
|
BORDER="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="25"
|
|
ALIGN="CENTER"
|
|
VALIGN="TOP"
|
|
><IMG
|
|
SRC="../images/note.gif"
|
|
HSPACE="5"
|
|
ALT="Note"></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><P
|
|
>When used in a non-interactive script,
|
|
<B
|
|
CLASS="COMMAND"
|
|
>mv</B
|
|
> takes the <TT
|
|
CLASS="OPTION"
|
|
>-f</TT
|
|
>
|
|
(<I
|
|
CLASS="FIRSTTERM"
|
|
>force</I
|
|
>) option to bypass user
|
|
input.</P
|
|
><P
|
|
>When a directory is moved to a preexisting directory,
|
|
it becomes a subdirectory of the destination directory.</P
|
|
><P
|
|
> <TABLE
|
|
BORDER="1"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="SCREEN"
|
|
><TT
|
|
CLASS="PROMPT"
|
|
>bash$ </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>mv source_directory target_directory</B
|
|
></TT
|
|
>
|
|
|
|
<TT
|
|
CLASS="PROMPT"
|
|
>bash$ </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>ls -lF target_directory</B
|
|
></TT
|
|
>
|
|
<TT
|
|
CLASS="COMPUTEROUTPUT"
|
|
>total 1
|
|
drwxrwxr-x 2 bozo bozo 1024 May 28 19:20 source_directory/</TT
|
|
>
|
|
</PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
>
|
|
</P
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="RMREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>rm</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
>Delete (remove) a file or files. The <TT
|
|
CLASS="OPTION"
|
|
>-f</TT
|
|
>
|
|
option forces removal of even readonly files, and is useful
|
|
for bypassing user input in a script.</P
|
|
><DIV
|
|
CLASS="NOTE"
|
|
><P
|
|
></P
|
|
><TABLE
|
|
CLASS="NOTE"
|
|
WIDTH="90%"
|
|
BORDER="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="25"
|
|
ALIGN="CENTER"
|
|
VALIGN="TOP"
|
|
><IMG
|
|
SRC="../images/note.gif"
|
|
HSPACE="5"
|
|
ALT="Note"></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><P
|
|
><A
|
|
NAME="DASHREM"
|
|
></A
|
|
></P
|
|
><P
|
|
>The <I
|
|
CLASS="FIRSTTERM"
|
|
>rm</I
|
|
> command will, by
|
|
itself, fail to remove filenames beginning with
|
|
a dash. Why? Because <I
|
|
CLASS="FIRSTTERM"
|
|
>rm</I
|
|
>
|
|
sees a dash-prefixed filename as an
|
|
<I
|
|
CLASS="FIRSTTERM"
|
|
>option</I
|
|
>.</P
|
|
><P
|
|
> <TABLE
|
|
BORDER="1"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="SCREEN"
|
|
><TT
|
|
CLASS="PROMPT"
|
|
>bash$ </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>rm -badname</B
|
|
></TT
|
|
>
|
|
<TT
|
|
CLASS="COMPUTEROUTPUT"
|
|
>rm: invalid option -- b
|
|
Try `rm --help' for more information.</TT
|
|
></PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
>
|
|
</P
|
|
><P
|
|
> One clever workaround is to precede
|
|
the filename with a <SPAN
|
|
CLASS="QUOTE"
|
|
>" -- "</SPAN
|
|
> (the
|
|
<I
|
|
CLASS="FIRSTTERM"
|
|
>end-of-options</I
|
|
> flag).
|
|
|
|
<TABLE
|
|
BORDER="1"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="SCREEN"
|
|
><TT
|
|
CLASS="PROMPT"
|
|
>bash$ </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>rm -- -badname</B
|
|
></TT
|
|
></PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
>
|
|
</P
|
|
><P
|
|
> Another method to is to preface the filename to be removed
|
|
with a <TT
|
|
CLASS="FILENAME"
|
|
>dot-slash</TT
|
|
> .
|
|
|
|
<TABLE
|
|
BORDER="1"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="SCREEN"
|
|
><TT
|
|
CLASS="PROMPT"
|
|
>bash$ </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>rm ./-badname</B
|
|
></TT
|
|
></PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
>
|
|
</P
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
><DIV
|
|
CLASS="WARNING"
|
|
><P
|
|
></P
|
|
><TABLE
|
|
CLASS="WARNING"
|
|
WIDTH="90%"
|
|
BORDER="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="25"
|
|
ALIGN="CENTER"
|
|
VALIGN="TOP"
|
|
><IMG
|
|
SRC="../images/warning.gif"
|
|
HSPACE="5"
|
|
ALT="Warning"></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><P
|
|
><A
|
|
NAME="RMRECURS"
|
|
></A
|
|
>When used with the
|
|
recursive flag <TT
|
|
CLASS="OPTION"
|
|
>-r</TT
|
|
>, this command removes
|
|
files all the way down the directory tree from the current
|
|
directory. A careless <B
|
|
CLASS="COMMAND"
|
|
>rm -rf *</B
|
|
> can wipe
|
|
out a big chunk of a directory structure.</P
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="RMDIRREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>rmdir</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
>Remove directory. The directory must be empty of
|
|
all files -- including <SPAN
|
|
CLASS="QUOTE"
|
|
>"invisible"</SPAN
|
|
>
|
|
<I
|
|
CLASS="FIRSTTERM"
|
|
>dotfiles</I
|
|
>
|
|
|
|
<A
|
|
NAME="AEN10228"
|
|
HREF="#FTN.AEN10228"
|
|
><SPAN
|
|
CLASS="footnote"
|
|
>[2]</SPAN
|
|
></A
|
|
>
|
|
|
|
-- for this command to succeed.</P
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="MKDIRREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>mkdir</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
>Make directory, creates a new directory. For example,
|
|
<TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>mkdir -p project/programs/December</B
|
|
></TT
|
|
>
|
|
creates the named directory. The
|
|
<TT
|
|
CLASS="REPLACEABLE"
|
|
><I
|
|
>-p</I
|
|
></TT
|
|
> option automatically creates
|
|
any necessary parent directories.</P
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="CHMODREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>chmod</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
>Changes the attributes of an existing file or directory
|
|
(see <A
|
|
HREF="internal.html#EX44"
|
|
>Example 15-14</A
|
|
>).</P
|
|
><P
|
|
><TABLE
|
|
BORDER="0"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="PROGRAMLISTING"
|
|
>chmod +x filename
|
|
# Makes "filename" executable for all users.
|
|
|
|
chmod u+s filename
|
|
# Sets "suid" bit on "filename" permissions.
|
|
# An ordinary user may execute "filename" with same privileges as the file's owner.
|
|
# (This does not apply to shell scripts.)</PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></P
|
|
><P
|
|
><TABLE
|
|
BORDER="0"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="PROGRAMLISTING"
|
|
>chmod 644 filename
|
|
# Makes "filename" readable/writable to owner, readable to others
|
|
#+ (octal mode).
|
|
|
|
chmod 444 filename
|
|
# Makes "filename" read-only for all.
|
|
# Modifying the file (for example, with a text editor)
|
|
#+ not allowed for a user who does not own the file (except for root),
|
|
#+ and even the file owner must force a file-save
|
|
#+ if she modifies the file.
|
|
# Same restrictions apply for deleting the file.</PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></P
|
|
><P
|
|
><TABLE
|
|
BORDER="0"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="PROGRAMLISTING"
|
|
>chmod 1777 directory-name
|
|
# Gives everyone read, write, and execute permission in directory,
|
|
#+ however also sets the "sticky bit".
|
|
# This means that only the owner of the directory,
|
|
#+ owner of the file, and, of course, root
|
|
#+ can delete any particular file in that directory.
|
|
|
|
chmod 111 directory-name
|
|
# Gives everyone execute-only permission in a directory.
|
|
# This means that you can execute and READ the files in that directory
|
|
#+ (execute permission necessarily includes read permission
|
|
#+ because you can't execute a file without being able to read it).
|
|
# But you can't list the files or search for them with the "find" command.
|
|
# These restrictions do not apply to root.
|
|
|
|
chmod 000 directory-name
|
|
# No permissions at all for that directory.
|
|
# Can't read, write, or execute files in it.
|
|
# Can't even list files in it or "cd" to it.
|
|
# But, you can rename (mv) the directory
|
|
#+ or delete it (rmdir) if it is empty.
|
|
# You can even symlink to files in the directory,
|
|
#+ but you can't read, write, or execute the symlinks.
|
|
# These restrictions do not apply to root.</PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></P
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="CHATTRREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>chattr</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
><B
|
|
CLASS="COMMAND"
|
|
>Ch</B
|
|
>ange file
|
|
<B
|
|
CLASS="COMMAND"
|
|
>attr</B
|
|
>ibutes. This is analogous to
|
|
<B
|
|
CLASS="COMMAND"
|
|
>chmod</B
|
|
> above, but with different options
|
|
and a different invocation syntax, and it works only on
|
|
<I
|
|
CLASS="FIRSTTERM"
|
|
>ext2/ext3</I
|
|
> filesystems.</P
|
|
><P
|
|
>One particularly interesting <B
|
|
CLASS="COMMAND"
|
|
>chattr</B
|
|
>
|
|
option is <TT
|
|
CLASS="OPTION"
|
|
>i</TT
|
|
>. A <B
|
|
CLASS="COMMAND"
|
|
>chattr +i
|
|
<TT
|
|
CLASS="FILENAME"
|
|
>filename</TT
|
|
></B
|
|
> marks the file
|
|
as immutable. The file cannot be modified, linked to, or
|
|
deleted, <EM
|
|
>not even by root</EM
|
|
>. This
|
|
file attribute can be set or removed only by
|
|
<I
|
|
CLASS="FIRSTTERM"
|
|
>root</I
|
|
>. In a similar fashion,
|
|
the <TT
|
|
CLASS="OPTION"
|
|
>a</TT
|
|
> option marks the file as append
|
|
only.</P
|
|
><P
|
|
> <TABLE
|
|
BORDER="1"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="SCREEN"
|
|
><TT
|
|
CLASS="PROMPT"
|
|
>root# </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>chattr +i file1.txt</B
|
|
></TT
|
|
>
|
|
|
|
|
|
<TT
|
|
CLASS="PROMPT"
|
|
>root# </TT
|
|
><TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>rm file1.txt</B
|
|
></TT
|
|
>
|
|
|
|
<TT
|
|
CLASS="COMPUTEROUTPUT"
|
|
>rm: remove write-protected regular file `file1.txt'? y
|
|
rm: cannot remove `file1.txt': Operation not permitted</TT
|
|
>
|
|
</PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
>
|
|
</P
|
|
><P
|
|
>If a file has the <TT
|
|
CLASS="OPTION"
|
|
>s</TT
|
|
> (secure)
|
|
attribute set, then when it is deleted its block is
|
|
overwritten with binary zeroes.
|
|
<A
|
|
NAME="AEN10301"
|
|
HREF="#FTN.AEN10301"
|
|
><SPAN
|
|
CLASS="footnote"
|
|
>[3]</SPAN
|
|
></A
|
|
>
|
|
</P
|
|
><P
|
|
>If a file has the <TT
|
|
CLASS="OPTION"
|
|
>u</TT
|
|
> (undelete)
|
|
attribute set, then when it is deleted, its contents can still
|
|
be retrieved (undeleted).</P
|
|
><P
|
|
>If a file has the <TT
|
|
CLASS="OPTION"
|
|
>c</TT
|
|
> (compress)
|
|
attribute set, then it will automatically be compressed
|
|
on writes to disk, and uncompressed on reads.</P
|
|
><DIV
|
|
CLASS="NOTE"
|
|
><P
|
|
></P
|
|
><TABLE
|
|
CLASS="NOTE"
|
|
WIDTH="90%"
|
|
BORDER="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="25"
|
|
ALIGN="CENTER"
|
|
VALIGN="TOP"
|
|
><IMG
|
|
SRC="../images/note.gif"
|
|
HSPACE="5"
|
|
ALT="Note"></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><P
|
|
>The file attributes set with
|
|
<B
|
|
CLASS="COMMAND"
|
|
>chattr</B
|
|
> do not show in a file listing
|
|
(<B
|
|
CLASS="COMMAND"
|
|
>ls -l</B
|
|
>).</P
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="LINKREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>ln</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
>Creates links to pre-existings files. A <SPAN
|
|
CLASS="QUOTE"
|
|
>"link"</SPAN
|
|
>
|
|
is a reference to a file, an alternate name for it.
|
|
The <B
|
|
CLASS="COMMAND"
|
|
>ln</B
|
|
> command permits referencing
|
|
the linked file by more than one name and is a superior
|
|
alternative to aliasing (see <A
|
|
HREF="othertypesv.html#EX18"
|
|
>Example 4-6</A
|
|
>).</P
|
|
><P
|
|
>The <B
|
|
CLASS="COMMAND"
|
|
>ln</B
|
|
> creates only a reference, a
|
|
pointer to the file only a few bytes in size.</P
|
|
><P
|
|
><A
|
|
NAME="SYMLINKREF"
|
|
></A
|
|
></P
|
|
><P
|
|
>The <B
|
|
CLASS="COMMAND"
|
|
>ln</B
|
|
> command is most often used
|
|
with the <TT
|
|
CLASS="OPTION"
|
|
>-s</TT
|
|
>, symbolic or
|
|
<SPAN
|
|
CLASS="QUOTE"
|
|
>"soft"</SPAN
|
|
> link flag. Advantages of using the
|
|
<TT
|
|
CLASS="OPTION"
|
|
>-s</TT
|
|
> flag are that it permits linking across
|
|
file systems or to directories.</P
|
|
><P
|
|
>The syntax of the command is a bit tricky. For example:
|
|
<TT
|
|
CLASS="USERINPUT"
|
|
><B
|
|
>ln -s oldfile newfile</B
|
|
></TT
|
|
> links the
|
|
previously existing <TT
|
|
CLASS="FILENAME"
|
|
>oldfile</TT
|
|
> to the
|
|
newly created link, <TT
|
|
CLASS="FILENAME"
|
|
>newfile</TT
|
|
>.</P
|
|
><DIV
|
|
CLASS="CAUTION"
|
|
><P
|
|
></P
|
|
><TABLE
|
|
CLASS="CAUTION"
|
|
WIDTH="90%"
|
|
BORDER="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="25"
|
|
ALIGN="CENTER"
|
|
VALIGN="TOP"
|
|
><IMG
|
|
SRC="../images/caution.gif"
|
|
HSPACE="5"
|
|
ALT="Caution"></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><P
|
|
>If a file named <TT
|
|
CLASS="FILENAME"
|
|
>newfile</TT
|
|
> has
|
|
previously existed, an error message will
|
|
result.</P
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
><TABLE
|
|
CLASS="SIDEBAR"
|
|
BORDER="1"
|
|
CELLPADDING="5"
|
|
><TR
|
|
><TD
|
|
><DIV
|
|
CLASS="SIDEBAR"
|
|
><A
|
|
NAME="AEN10336"
|
|
></A
|
|
><P
|
|
><B
|
|
>Which type of link to use?</B
|
|
></P
|
|
><P
|
|
>As John Macdonald explains it:</P
|
|
><P
|
|
>Both of these [types of links] provide a certain measure of dual reference
|
|
-- if you edit the contents of the file using any name,
|
|
your changes will affect both the original name and either
|
|
a hard or soft new name. The differences between them
|
|
occurs when you work at a higher level. The advantage of
|
|
a hard link is that the new name is totally independent
|
|
of the old name -- if you remove or rename the old name,
|
|
that does not affect the hard link, which continues
|
|
to point to the data while it would leave a soft link
|
|
hanging pointing to the old name which is no longer
|
|
there. The advantage of a soft link is that it can refer
|
|
to a different file system (since it is just a reference
|
|
to a file name, not to actual data). And, unlike a hard
|
|
link, a symbolic link can refer to a directory.</P
|
|
></DIV
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
><P
|
|
><A
|
|
NAME="LINKMINVOK"
|
|
></A
|
|
></P
|
|
><P
|
|
>Links give the ability to invoke a script (or any other type
|
|
of executable) with multiple names, and having that script
|
|
behave according to how it was invoked.</P
|
|
><DIV
|
|
CLASS="EXAMPLE"
|
|
><A
|
|
NAME="HELLOL"
|
|
></A
|
|
><P
|
|
><B
|
|
>Example 16-2. Hello or Good-bye</B
|
|
></P
|
|
><TABLE
|
|
BORDER="0"
|
|
BGCOLOR="#E0E0E0"
|
|
WIDTH="90%"
|
|
><TR
|
|
><TD
|
|
><FONT
|
|
COLOR="#000000"
|
|
><PRE
|
|
CLASS="PROGRAMLISTING"
|
|
>#!/bin/bash
|
|
# hello.sh: Saying "hello" or "goodbye"
|
|
#+ depending on how script is invoked.
|
|
|
|
# Make a link in current working directory ($PWD) to this script:
|
|
# ln -s hello.sh goodbye
|
|
# Now, try invoking this script both ways:
|
|
# ./hello.sh
|
|
# ./goodbye
|
|
|
|
|
|
HELLO_CALL=65
|
|
GOODBYE_CALL=66
|
|
|
|
if [ $0 = "./goodbye" ]
|
|
then
|
|
echo "Good-bye!"
|
|
# Some other goodbye-type commands, as appropriate.
|
|
exit $GOODBYE_CALL
|
|
fi
|
|
|
|
echo "Hello!"
|
|
# Some other hello-type commands, as appropriate.
|
|
exit $HELLO_CALL</PRE
|
|
></FONT
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
></DD
|
|
><DT
|
|
><A
|
|
NAME="MANREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>man</B
|
|
>, <A
|
|
NAME="INFOREF"
|
|
></A
|
|
><B
|
|
CLASS="COMMAND"
|
|
>info</B
|
|
></DT
|
|
><DD
|
|
><P
|
|
>These commands access the manual and information pages on
|
|
system commands and installed utilities. When available, the
|
|
<I
|
|
CLASS="FIRSTTERM"
|
|
>info</I
|
|
> pages usually contain more detailed
|
|
descriptions than do the <I
|
|
CLASS="FIRSTTERM"
|
|
>man</I
|
|
> pages.</P
|
|
><P
|
|
>There have been various attempts at
|
|
<SPAN
|
|
CLASS="QUOTE"
|
|
>"automating"</SPAN
|
|
> the writing of <I
|
|
CLASS="FIRSTTERM"
|
|
>man
|
|
pages</I
|
|
>. For a script that makes a tentative first
|
|
step in that direction, see <A
|
|
HREF="contributed-scripts.html#MANED"
|
|
>Example A-39</A
|
|
>.</P
|
|
></DD
|
|
></DL
|
|
></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.AEN10025"
|
|
HREF="basic.html#AEN10025"
|
|
><SPAN
|
|
CLASS="footnote"
|
|
>[1]</SPAN
|
|
></A
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
WIDTH="95%"
|
|
><P
|
|
>The <TT
|
|
CLASS="OPTION"
|
|
>-v</TT
|
|
> option also orders the
|
|
sort by <EM
|
|
>upper- and lowercase prefixed</EM
|
|
>
|
|
filenames.</P
|
|
></TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
WIDTH="5%"
|
|
><A
|
|
NAME="FTN.AEN10228"
|
|
HREF="basic.html#AEN10228"
|
|
><SPAN
|
|
CLASS="footnote"
|
|
>[2]</SPAN
|
|
></A
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
WIDTH="95%"
|
|
><P
|
|
><A
|
|
NAME="DOTFILESREF"
|
|
></A
|
|
></P
|
|
><P
|
|
><I
|
|
CLASS="FIRSTTERM"
|
|
>Dotfiles</I
|
|
> are files whose
|
|
names begin with a <I
|
|
CLASS="FIRSTTERM"
|
|
>dot</I
|
|
>, such as
|
|
<TT
|
|
CLASS="FILENAME"
|
|
>~/.Xdefaults</TT
|
|
>. Such filenames do
|
|
not appear in a normal <B
|
|
CLASS="COMMAND"
|
|
>ls</B
|
|
> listing
|
|
(although an <B
|
|
CLASS="COMMAND"
|
|
>ls -a</B
|
|
> will show
|
|
them), and they cannot be deleted by an accidental
|
|
<B
|
|
CLASS="COMMAND"
|
|
>rm -rf *</B
|
|
>. Dotfiles are generally
|
|
used as setup and configuration files in a user's
|
|
home directory.</P
|
|
></TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
WIDTH="5%"
|
|
><A
|
|
NAME="FTN.AEN10301"
|
|
HREF="basic.html#AEN10301"
|
|
><SPAN
|
|
CLASS="footnote"
|
|
>[3]</SPAN
|
|
></A
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
WIDTH="95%"
|
|
><P
|
|
>This particular feature may not yet be
|
|
implemented in the version of the ext2/ext3 filesystem
|
|
installed on your system. Check the documentation for
|
|
your Linux distro.</P
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
><DIV
|
|
CLASS="NAVFOOTER"
|
|
><HR
|
|
ALIGN="LEFT"
|
|
WIDTH="100%"><TABLE
|
|
SUMMARY="Footer navigation table"
|
|
WIDTH="100%"
|
|
BORDER="0"
|
|
CELLPADDING="0"
|
|
CELLSPACING="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="left"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="external.html"
|
|
ACCESSKEY="P"
|
|
>Prev</A
|
|
></TD
|
|
><TD
|
|
WIDTH="34%"
|
|
ALIGN="center"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="index.html"
|
|
ACCESSKEY="H"
|
|
>Home</A
|
|
></TD
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="right"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="moreadv.html"
|
|
ACCESSKEY="N"
|
|
>Next</A
|
|
></TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="left"
|
|
VALIGN="top"
|
|
>External Filters, Programs and Commands</TD
|
|
><TD
|
|
WIDTH="34%"
|
|
ALIGN="center"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="external.html"
|
|
ACCESSKEY="U"
|
|
>Up</A
|
|
></TD
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="right"
|
|
VALIGN="top"
|
|
>Complex Commands</TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
></BODY
|
|
></HTML
|
|
> |