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BASH Shell 编程经典教程《高级SHELL脚本编程》中文版
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><HTML><HEAD><TITLE>Here String</TITLE><METANAME="GENERATOR"CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINKREL="HOME"TITLE="高级Bash脚本编程指南"HREF="index.html"><LINKREL="UP"TITLE="Here Document"HREF="here-docs.html"><LINKREL="PREVIOUS"TITLE="Here Document"HREF="here-docs.html"><LINKREL="NEXT"TITLE="休息片刻"HREF="recess-time.html"></HEAD><BODYCLASS="SECT1"BGCOLOR="#FFFFFF"TEXT="#000000"LINK="#0000FF"VLINK="#840084"ALINK="#0000FF"><DIVCLASS="NAVHEADER"><TABLESUMMARY="Header navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><THCOLSPAN="3"ALIGN="center">高级Bash脚本编程指南: 一本深入学习shell脚本艺术的书籍</TH></TR><TR><TDWIDTH="10%"ALIGN="left"VALIGN="bottom"><AHREF="here-docs.html"ACCESSKEY="P">前一页</A></TD><TDWIDTH="80%"ALIGN="center"VALIGN="bottom">17. Here Document</TD><TDWIDTH="10%"ALIGN="right"VALIGN="bottom"><AHREF="recess-time.html"ACCESSKEY="N">下一页</A></TD></TR></TABLE><HRALIGN="LEFT"WIDTH="100%"></DIV><DIVCLASS="SECT1"><H1CLASS="SECT1"><ANAME="AEN13590">17.1. Here String</A></H1><P><ANAME="HERESTRINGSREF"></A></P><P><ICLASS="FIRSTTERM">here string</I>可以看成是<ICLASS="FIRSTTERM">here document</I>的一种定制形式. 			 除了<BCLASS="COMMAND">COMMAND &#60;&#60;&#60;$WORD</B>, 就什么都没有了, 			<CODECLASS="VARNAME">$WORD</CODE>将被扩展并且被送入<CODECLASS="VARNAME">COMMAND</CODE>的<TTCLASS="FILENAME">stdin</TT>中. </P><P>	<TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><FONTCOLOR="#000000"><PRECLASS="PROGRAMLISTING">String="This is a string of words."read -r -a Words &#60;&#60;&#60; "$String"#  "read"命令的-a选项#+ 将会把结果值按顺序的分配给数组中的每一项. echo "First word in String is:    ${Words[0]}"   # Thisecho "Second word in String is:   ${Words[1]}"   # isecho "Third word in String is:    ${Words[2]}"   # aecho "Fourth word in String is:   ${Words[3]}"   # stringecho "Fifth word in String is:    ${Words[4]}"   # ofecho "Sixth word in String is:    ${Words[5]}"   # words.echo "Seventh word in String is:  ${Words[6]}"   # (null)                                                 # $String的结尾. # 感谢, Francisco Lobo的这个建议. </PRE></FONT></TD></TR></TABLE>        </P><DIVCLASS="EXAMPLE"><HR><ANAME="PREPENDEX"></A><P><B>例子 17-13. 在一个文件的开头添加文本</B></P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><FONTCOLOR="#000000"><PRECLASS="PROGRAMLISTING">#!/bin/bash# prepend.sh: 在文件的开头添加文本. ##  Kenny Stauffer所捐助的脚本例子, #+ 本文作者对这个脚本进行了少量修改. E_NOSUCHFILE=65read -p "File: " file   #  'read'命令的-p参数用来显示提示符. if [ ! -e "$file" ]then   # 如果这个文件不存在, 那就进来.   echo "File $file not found."  exit $E_NOSUCHFILEfiread -p "Title: " titlecat - $file &#60;&#60;&#60;$title &#62; $file.newecho "Modified file is $file.new"exit 0# 下边是'man bash'中的一段: # Here String# 	here document的一种变形，形式如下: # # 		&#60;&#60;&#60;word# # 	word被扩展并且被提供到command的标准输入中. </PRE></FONT></TD></TR></TABLE><HR></DIV><DIVCLASS="EXAMPLE"><HR><ANAME="MAILBOXGREP"></A><P><B>例子 17-14. 分析一个邮箱</B></P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><FONTCOLOR="#000000"><PRECLASS="PROGRAMLISTING">#!/bin/bash#  由Francisco Lobo所提供的脚本, #+ 本文作者进行了少量修改和注释. #  并且经过授权, 可以使用在本书中.(感谢你!)# 这个脚本不能运行于比Bash version 3.0更低的版本中. E_MISSING_ARG=67if [ -z "$1" ]then  echo "Usage: $0 mailbox-file"  exit $E_MISSING_ARGfimbox_grep()  # 分析邮箱文件.{    declare -i body=0 match=0    declare -a date sender    declare mail header value    while IFS= read -r mail#         ^^^^                 重新设置$IFS.#  否则"read"会从它的输入中截去开头和结尾的空格.    do       if [[ $mail =~ "^From " ]]   # 匹配消息中的"From"域.        then          (( body  = 0 ))           # 取消("Zero out"俚语)变量.           (( match = 0 ))          unset date       elif (( body ))       then            (( match ))            # echo "$mail"            # 如果你想显示整个消息体的话, 那么就打开上面的注释行.        elif [[ $mail ]]; then          IFS=: read -r header value &#60;&#60;&#60; "$mail"          #                          ^^^  "here string"          case "$header" in          [Ff][Rr][Oo][Mm] ) [[ $value =~ "$2" ]] &#38;&#38; (( match++ )) ;;          # 匹配"From"行.           [Dd][Aa][Tt][Ee] ) read -r -a date &#60;&#60;&#60; "$value" ;;          #                                  ^^^          # 匹配"Date"行.           [Rr][Ee][Cc][Ee][Ii][Vv][Ee][Dd] ) read -r -a sender &#60;&#60;&#60; "$value" ;;          #                                                    ^^^          # 匹配IP地址(可能被欺骗).           esac       else          (( body++ ))          (( match  )) &#38;&#38;          echo "MESSAGE ${date:+of: ${date[*]} }"       #    整个$date数组                  ^          echo "IP address of sender: ${sender[1]}"       #    "Received"行的第二个域             ^       fi    done &#60; "$1" # 将文件的stdout重定向到循环中. }mbox_grep "$1"  # 将邮箱文件发送到函数中. exit $?# 练习:# -----# 1) 拆开上面的这个函数, 把它分成多个函数, #+   这样可以提高代码的可读性. # 2) 对这个脚本添加额外的分析, 可以分析不同的关键字. $ mailbox_grep.sh scam_mail--&#62; MESSAGE of Thu, 5 Jan 2006 08:00:56 -0500 (EST) --&#62; IP address of sender: 196.3.62.4</PRE></FONT></TD></TR></TABLE><HR></DIV><P>练习: 找出<EM>here string</EM>的其他用法. </P></DIV><DIVCLASS="NAVFOOTER"><HRALIGN="LEFT"WIDTH="100%"><TABLESUMMARY="Footer navigation table"WIDTH="100%"BORDER="0"CELLPADDING="0"CELLSPACING="0"><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top"><AHREF="here-docs.html"ACCESSKEY="P">前一页</A></TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="index.html"ACCESSKEY="H">首页</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top"><AHREF="recess-time.html"ACCESSKEY="N">下一页</A></TD></TR><TR><TDWIDTH="33%"ALIGN="left"VALIGN="top">Here Document</TD><TDWIDTH="34%"ALIGN="center"VALIGN="top"><AHREF="here-docs.html"ACCESSKEY="U">上一级</A></TD><TDWIDTH="33%"ALIGN="right"VALIGN="top">休息片刻</TD></TR></TABLE></DIV></BODY></HTML>
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