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website/content/ChapterFive/Chongdingxiang1.md

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+---
+title: 1.01  常规重定向
+type: docs
+weight: 1
+---
+
+|重定向式子|作用|
+|:---:|:---:|   
+|1>file|重定向stdout到file|
+|2>file|重定向stderr到file|
+|0>file|重定向stdin到file|
+|&>file|重定向stdout和stderr到file|
+|2>&1|重定向stderr到stdout|
+|i>&j|指向i文件的所有输出发送到j中|
+|>&j|默认重定向描述符1的输出发送到j中|
+|[i]<>file|分配文件描述符i给file|
+|\||管道|
+|n<&-|关闭输入文件标识符n|
+|n>&-|关闭输出文件标识符n|
+
+
+<div style="display: flex;justify-content: space-between;align-items: center;">
+<p><a href="https://books.linuxwt.com/linuxwtabs/ChapterFive">上一页➡️</a></p>
+<p><a href="https://books.linuxwt.com/linuxwtabs/ChapterFive/Chongdingxiang2">下一页➡️</a></p>
+</div>

website/content/ChapterFive/Chongdingxiang2.md

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+---
+title: 1.02  重定向中的exec
+type: docs
+weight: 1
+---
+
+# exec重定向标准输入
+```bash
+#!/bin/bash
+
+exec 6<&0 # 将stdin重定向到文件标识符6
+exec < test.txt # 使用test.txt文件内容代替stdin，即后面的输入全部来自该文件
+read a1 # 读取test.txt第一行
+read a2 
+
+echo "Following lines read from file"
+echo "--------"
+echo $a1
+echo $a2
+
+exec 0<&6 6<&-  # 从文件标识符6恢复stdin并关闭文件标识符6
+echo "enter data"
+read b1
+echo "Input read from stdin"
+echo "--------"
+echo $b1
+
+exit 0
+```   
+
+# exec重定向标准输出   
+```bash
+#!/bin/bash
+
+exec 6>&1   # 将标准输出重定向到文件标识符6
+exec > test1.txt # 输出到stdout的内容全部输出到文件test1.txt
+
+echo "logfile"
+date
+echo "------------"
+
+echo "output of \"ls -la\" command"
+ls -la
+echo "output of \"df\" command"
+df
+
+exec 1>&6 6>&- # 从文件标识符6恢复stdout并关闭文件标识符6
+
+echo "stdout now restored to default"
+echo "------------"
+ls -la
+
+exit 0
+```   
+
+# exec同时重定向标准输入标准输出   
+```bash
+#!/bin/bash
+
+E_FILE_ACCESS=70
+E_WRONG_ARGS=71
+
+if [ ! -r "$1" ]
+then
+  echo "can not read from inputfile"
+  echo "Usage :$0 input file"
+ exit $E_FILE_ACCESS
+fi
+
+if [ -z "$2" ]
+then
+  echo "need to specify output file"
+  echo "Usage: $0 inputfile outputfile"
+  exit $E_WRONG_ARGS
+fi
+
+exec 4<&0
+exec < $1
+
+exec 6>&1
+exec > $2
+
+cat - | tr a-z A-Z # 从$1处获得输入并将其中小写字符转换成大写
+
+exec 0<&4 4<&-
+exec 1>&6 6>&-
+
+echo "File \"$1\" written to \"$2\""
+```   
+这个脚本需要事先创建一个文件   
+cat test2.txt   
+```bash
+a
+b
+c
+```   
+
+bash 3.sh test2.txt test3.txt   
+
+
+<div style="display: flex;justify-content: space-between;align-items: center;">
+<p><a href="https://books.linuxwt.com/linuxwtabs/ChapterFive/Chongdingxiang1">上一页➡️</a></p>
+<p><a href="https://books.linuxwt.com/linuxwtabs/ChapterSix">下一章➡️</a></p>
+</div>

website/content/ChapterFive/_index.md

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+---
+title: 第四章 重定向
+type: docs
+weight: 5
+---   
+
+ 重定向：捕捉文件、命令、程序、脚本的输出，然后将这些输出发送到另外一个文件、命令、程序、脚本中
+
+<div style="display: flex;justify-content: space-between;align-items: center;">
+<p><a href="https://books.linuxwt.com/linuxwtabs/ChapterFour/Subshell3">上一页➡️</a></p>
+<p><a href="https://books.linuxwt.com/linuxwtabs/ChapterFive/Chongdingxiang1">下一页➡️</a></p>
+</div>

website/content/ChapterFour/Subshell3.md

@@ -19,5 +19,5 @@ diff list123 list456
 
 <div style="display: flex;justify-content: space-between;align-items: center;">
 <p><a href="https://books.linuxwt.com/linuxwtabs/ChapterFour/Subshell2">上一页➡️</a></p>
-<p><a href="https://books.linuxwt.com/linuxwtabs/ChapterThree">下一章➡️</a></p>
+<p><a href="https://books.linuxwt.com/linuxwtabs/ChapterFive">下一章➡️</a></p>
 </div>