948 lines
12 KiB
HTML
948 lines
12 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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>Options</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="Advanced Topics"
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HREF="part5.html"><LINK
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REL="PREVIOUS"
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TITLE="Debugging"
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HREF="debugging.html"><LINK
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REL="NEXT"
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TITLE="Gotchas"
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HREF="gotchas.html"></HEAD
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><BODY
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CLASS="CHAPTER"
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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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SUMMARY="Header navigation table"
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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="debugging.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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></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="gotchas.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="CHAPTER"
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><H1
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><A
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NAME="OPTIONS"
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></A
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>Chapter 33. Options</H1
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><P
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><A
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NAME="OPTIONSREF"
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></A
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></P
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><P
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>Options are settings that change shell and/or script
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behavior.</P
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><P
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>The <A
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HREF="internal.html#SETREF"
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>set</A
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> command
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enables options within a script. At the point in the script
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where you want the options to take effect, use <B
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CLASS="COMMAND"
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>set
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-o option-name</B
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> or, in short form, <B
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CLASS="COMMAND"
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>set
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-option-abbrev</B
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>. These two forms are equivalent.</P
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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="100%"
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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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set -o verbose
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# Echoes all commands before executing.
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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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><P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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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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set -v
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# Exact same effect as above.
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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="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="100%"
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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"
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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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>To <I
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CLASS="FIRSTTERM"
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>disable</I
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> an option within a script,
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use <B
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CLASS="COMMAND"
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>set +o option-name</B
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> or <B
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CLASS="COMMAND"
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>set
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+option-abbrev</B
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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
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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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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set -o verbose
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# Command echoing on.
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command
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...
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command
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set +o verbose
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# Command echoing off.
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command
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# Not echoed.
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set -v
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# Command echoing on.
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command
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...
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command
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set +v
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# Command echoing off.
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command
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exit 0
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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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><P
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>An alternate method of enabling options in a script is
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to specify them immediately following the
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<TT
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CLASS="REPLACEABLE"
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><I
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>#!</I
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></TT
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> script header.</P
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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="100%"
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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 -x
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#
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# Body of script follows.
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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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><P
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><A
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NAME="INVOCATIONOPTIONSREF"
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></A
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></P
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><P
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>It is also possible to enable script options from the command
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line. Some options that will not work with
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<B
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CLASS="COMMAND"
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>set</B
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> are available this way. Among these
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are <TT
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CLASS="REPLACEABLE"
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><I
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>-i</I
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></TT
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>, force script to run
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interactive.</P
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><P
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><TT
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CLASS="USERINPUT"
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><B
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>bash -v script-name</B
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></TT
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></P
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><P
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><TT
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CLASS="USERINPUT"
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><B
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>bash -o verbose script-name</B
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></TT
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></P
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><P
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>The following is a listing of some useful options. They may be
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specified in either abbreviated form (preceded by a single dash)
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or by complete name (preceded by a <EM
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>double</EM
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>
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dash or by <TT
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CLASS="OPTION"
|
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>-o</TT
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>).</P
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><P
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><A
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NAME="OPTIONSTABLE"
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></A
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></P
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><DIV
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CLASS="TABLE"
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><A
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NAME="AEN19601"
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></A
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><P
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><B
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>Table 33-1. Bash 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="TOP"
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>Abbreviation</TH
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><TH
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ALIGN="LEFT"
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VALIGN="TOP"
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>Name</TH
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><TH
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ALIGN="LEFT"
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VALIGN="TOP"
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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="TOP"
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><TT
|
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CLASS="OPTION"
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>-B</TT
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></TD
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><TD
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ALIGN="LEFT"
|
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VALIGN="TOP"
|
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>brace expansion</TD
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><TD
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|
ALIGN="LEFT"
|
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VALIGN="TOP"
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><EM
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>Enable</EM
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>
|
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<A
|
|
HREF="special-chars.html#BRACEEXPREF"
|
|
>brace
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expansion</A
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> (default setting =
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<EM
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>on</EM
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>)</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="TOP"
|
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><TT
|
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CLASS="OPTION"
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>+B</TT
|
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></TD
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><TD
|
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ALIGN="LEFT"
|
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VALIGN="TOP"
|
|
>brace expansion</TD
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><TD
|
|
ALIGN="LEFT"
|
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VALIGN="TOP"
|
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><EM
|
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>Disable</EM
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>
|
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brace expansion</TD
|
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></TR
|
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><TR
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><TD
|
|
ALIGN="LEFT"
|
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VALIGN="TOP"
|
|
><A
|
|
NAME="NOCLOBBERREF"
|
|
></A
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-C</TT
|
|
></TD
|
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><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
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>noclobber</TD
|
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><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Prevent overwriting of files by redirection (may be
|
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overridden by <SPAN
|
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CLASS="TOKEN"
|
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>>|</SPAN
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|
>)</TD
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></TR
|
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><TR
|
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><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-D</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
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>(none)</TD
|
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><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>List double-quoted strings prefixed by <SPAN
|
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CLASS="TOKEN"
|
|
>$</SPAN
|
|
>,
|
|
but do not execute commands in script</TD
|
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></TR
|
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><TR
|
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><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-a</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>allexport</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Export all defined variables</TD
|
|
></TR
|
|
><TR
|
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><TD
|
|
ALIGN="LEFT"
|
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VALIGN="TOP"
|
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><TT
|
|
CLASS="OPTION"
|
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>-b</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
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VALIGN="TOP"
|
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>notify</TD
|
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><TD
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|
ALIGN="LEFT"
|
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VALIGN="TOP"
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>Notify when jobs running in background terminate (not of
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much use in a script)</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="TOP"
|
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><TT
|
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CLASS="OPTION"
|
|
>-c ...</TT
|
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></TD
|
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><TD
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ALIGN="LEFT"
|
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VALIGN="TOP"
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>(none)</TD
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><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
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>Read commands from <B
|
|
CLASS="COMMAND"
|
|
>...</B
|
|
></TD
|
|
></TR
|
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><TR
|
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><TD
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|
ALIGN="LEFT"
|
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VALIGN="TOP"
|
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><TT
|
|
CLASS="OPTION"
|
|
>checkjobs</TT
|
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></TD
|
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><TD
|
|
ALIGN="LEFT"
|
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VALIGN="TOP"
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> </TD
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><TD
|
|
ALIGN="LEFT"
|
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VALIGN="TOP"
|
|
>Informs user of any open <A
|
|
HREF="x9644.html#JOBSREF"
|
|
>jobs</A
|
|
> upon shell exit.
|
|
Introduced in <A
|
|
HREF="bashver4.html#BASH4REF"
|
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>version 4</A
|
|
>
|
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of Bash, and still <SPAN
|
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CLASS="QUOTE"
|
|
>"experimental."</SPAN
|
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>
|
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<EM
|
|
>Usage:</EM
|
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> shopt -s checkjobs
|
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(<EM
|
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>Caution:</EM
|
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> may hang!)</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="TOP"
|
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><TT
|
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CLASS="OPTION"
|
|
>-e</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
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VALIGN="TOP"
|
|
>errexit</TD
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><TD
|
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ALIGN="LEFT"
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|
VALIGN="TOP"
|
|
>Abort script at first error, when a command
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exits with non-zero status (except in <A
|
|
HREF="loops1.html#UNTILLOOPREF"
|
|
>until</A
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> or <A
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HREF="loops1.html#WHILELOOPREF"
|
|
>while loops</A
|
|
>, <A
|
|
HREF="testconstructs.html#TESTCONSTRUCTS1"
|
|
>if-tests</A
|
|
>, <A
|
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HREF="list-cons.html#LCONS1"
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>list constructs</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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ALIGN="LEFT"
|
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VALIGN="TOP"
|
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><TT
|
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CLASS="OPTION"
|
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>-f</TT
|
|
></TD
|
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><TD
|
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ALIGN="LEFT"
|
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VALIGN="TOP"
|
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>noglob</TD
|
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><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Filename expansion (globbing) disabled</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>globstar</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><A
|
|
HREF="bashver4.html#GLOBSTARREF"
|
|
><I
|
|
CLASS="FIRSTTERM"
|
|
>globbing</I
|
|
>
|
|
star-match</A
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Enables the <SPAN
|
|
CLASS="TOKEN"
|
|
>**</SPAN
|
|
> <A
|
|
HREF="globbingref.html"
|
|
>globbing</A
|
|
> operator
|
|
(<A
|
|
HREF="bashver4.html#BASH4REF"
|
|
>version 4+</A
|
|
> of Bash).
|
|
<EM
|
|
>Usage:</EM
|
|
> shopt -s globstar</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-i</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>interactive</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Script runs in <I
|
|
CLASS="FIRSTTERM"
|
|
>interactive</I
|
|
> mode</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-n</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>noexec</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Read commands in script, but do not execute them (syntax check)</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-o Option-Name</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>(none)</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Invoke the <I
|
|
CLASS="FIRSTTERM"
|
|
>Option-Name</I
|
|
>
|
|
option</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-o posix</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>POSIX</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Change the behavior of Bash, or invoked script, to
|
|
conform to <A
|
|
HREF="sha-bang.html#POSIX2REF"
|
|
>POSIX</A
|
|
>
|
|
standard.</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-o pipefail</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>pipe failure</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Causes a pipeline to return the <A
|
|
HREF="exit-status.html#EXITSTATUSREF"
|
|
>exit status</A
|
|
> of
|
|
the last command in the pipe that returned a non-zero
|
|
return value.</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-p</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>privileged</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Script runs as <SPAN
|
|
CLASS="QUOTE"
|
|
>"suid"</SPAN
|
|
> (caution!)</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-r</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>restricted</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Script runs in <I
|
|
CLASS="FIRSTTERM"
|
|
>restricted</I
|
|
>
|
|
mode (see <A
|
|
HREF="restricted-sh.html"
|
|
>Chapter 22</A
|
|
>).</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-s</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>stdin</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Read commands from <TT
|
|
CLASS="FILENAME"
|
|
>stdin</TT
|
|
></TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-t</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>(none)</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Exit after first command</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-u</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>nounset</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Attempt to use undefined variable
|
|
outputs error message, and forces an exit</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-v</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>verbose</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Print each command to <TT
|
|
CLASS="FILENAME"
|
|
>stdout</TT
|
|
> before executing it</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-x</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>xtrace</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Similar to <TT
|
|
CLASS="OPTION"
|
|
>-v</TT
|
|
>, but expands commands</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>-</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>(none)</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>End of options flag. All other arguments
|
|
are <A
|
|
HREF="internalvariables.html#POSPARAMREF"
|
|
>positional
|
|
parameters</A
|
|
>.</TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><TT
|
|
CLASS="OPTION"
|
|
>--</TT
|
|
></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>(none)</TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
>Unset positional parameters.
|
|
If arguments given (<TT
|
|
CLASS="PARAMETER"
|
|
><I
|
|
>-- arg1 arg2</I
|
|
></TT
|
|
>),
|
|
positional parameters set to arguments.</TD
|
|
></TR
|
|
></TBODY
|
|
></TABLE
|
|
></DIV
|
|
></DIV
|
|
><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="debugging.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="gotchas.html"
|
|
ACCESSKEY="N"
|
|
>Next</A
|
|
></TD
|
|
></TR
|
|
><TR
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="left"
|
|
VALIGN="top"
|
|
>Debugging</TD
|
|
><TD
|
|
WIDTH="34%"
|
|
ALIGN="center"
|
|
VALIGN="top"
|
|
><A
|
|
HREF="part5.html"
|
|
ACCESSKEY="U"
|
|
>Up</A
|
|
></TD
|
|
><TD
|
|
WIDTH="33%"
|
|
ALIGN="right"
|
|
VALIGN="top"
|
|
>Gotchas</TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
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></BODY
|
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></HTML
|
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> |