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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="AEN13628">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 <<<$WORD</B>, 就什么都没有了, <CODECLASS="VARNAME">$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"> 1 String="This is a string of words." 2 3 read -r -a Words <<< "$String" 4 # "read"命令的-a选项 5 #+ 将会把结果值按顺序的分配给数组中的每一项. 6 7 echo "First word in String is: ${Words[0]}" # This 8 echo "Second word in String is: ${Words[1]}" # is 9 echo "Third word in String is: ${Words[2]}" # a 10 echo "Fourth word in String is: ${Words[3]}" # string 11 echo "Fifth word in String is: ${Words[4]}" # of 12 echo "Sixth word in String is: ${Words[5]}" # words. 13 echo "Seventh word in String is: ${Words[6]}" # (null) 14 # $String的结尾. 15 16 # 感谢, Francisco Lobo的这个建议. </PRE></FONT></TD></TR></TABLE> </P><DIVCLASS="EXAMPLE"><HR><ANAME="PREPENDEX"></A><P><B>例子 17-13. 在一个文件的开头添加文本</B></P><TABLEBORDER="0"BGCOLOR="#E0E0E0"WIDTH="100%"><TR><TD><FONTCOLOR="#000000"><PRECLASS="PROGRAMLISTING"> 1 #!/bin/bash 2 # prepend.sh: 在文件的开头添加文本. 3 # 4 # Kenny Stauffer所捐助的脚本例子, 5 #+ 本文作者对这个脚本进行了少量修改. 6 7 8 E_NOSUCHFILE=65 9 10 read -p "File: " file # 'read'命令的-p参数用来显示提示符. 11 if [ ! -e "$file" ] 12 then # 如果这个文件不存在, 那就进来. 13 echo "File $file not found." 14 exit $E_NOSUCHFILE 15 fi 16 17 read -p "Title: " title 18 cat - $file <<<$title > $file.new 19 20 echo "Modified file is $file.new" 21 22 exit 0 23 24 # 下边是'man bash'中的一段: 25 # Here String 26 # here document的一种变形，形式如下: 27 # 28 # <<<word 29 # 30 # 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"> 1 #!/bin/bash 2 # 由Francisco Lobo所提供的脚本, 3 #+ 本文作者进行了少量修改和注释. 4 # 并且经过授权, 可以使用在本书中.(感谢你!) 5 6 # 这个脚本不能运行于比Bash version 3.0更低的版本中. 7 8 9 E_MISSING_ARG=67 10 if [ -z "$1" ] 11 then 12 echo "Usage: $0 mailbox-file" 13 exit $E_MISSING_ARG 14 fi 15 16 mbox_grep() # 分析邮箱文件. 17 { 18 declare -i body=0 match=0 19 declare -a date sender 20 declare mail header value 21 22 23 while IFS= read -r mail 24 # ^^^^ 重新设置$IFS. 25 # 否则"read"会从它的输入中截去开头和结尾的空格. 26 27 do 28 if [[ $mail =~ "^From " ]] # 匹配消息中的"From"域. 29 then 30 (( body = 0 )) # 取消("Zero out"俚语)变量. 31 (( match = 0 )) 32 unset date 33 34 elif (( body )) 35 then 36 (( match )) 37 # echo "$mail" 38 # 如果你想显示整个消息体的话, 那么就打开上面的注释行. 39 40 elif [[ $mail ]]; then 41 IFS=: read -r header value <<< "$mail" 42 # ^^^ "here string" 43 44 case "$header" in 45 [Ff][Rr][Oo][Mm] ) [[ $value =~ "$2" ]] && (( match++ )) ;; 46 # 匹配"From"行. 47 [Dd][Aa][Tt][Ee] ) read -r -a date <<< "$value" ;; 48 # ^^^ 49 # 匹配"Date"行. 50 [Rr][Ee][Cc][Ee][Ii][Vv][Ee][Dd] ) read -r -a sender <<< "$value" ;; 51 # ^^^ 52 # 匹配IP地址(可能被欺骗). 53 esac 54 55 else 56 (( body++ )) 57 (( match )) && 58 echo "MESSAGE ${date:+of: ${date[*]} }" 59 # 整个$date数组 ^ 60 echo "IP address of sender: ${sender[1]}" 61 # "Received"行的第二个域 ^ 62 63 fi 64 65 66 done < "$1" # 将文件的stdout重定向到循环中. 67 } 68 69 70 mbox_grep "$1" # 将邮箱文件发送到函数中. 71 72 exit $? 73 74 # 练习: 75 # ----- 76 # 1) 拆开上面的这个函数, 把它分成多个函数, 77 #+ 这样可以提高代码的可读性. 78 # 2) 对这个脚本添加额外的分析, 可以分析不同的关键字. 79 80 81 82 $ mailbox_grep.sh scam_mail 83 --> MESSAGE of Thu, 5 Jan 2006 08:00:56 -0500 (EST) 84 --> 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>⌨️ 快捷键说明
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