2016-05-13

基本脚本/exit命令.sh

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+#!/bin/bash
+#退出状态码，最大为255，超过则进行模运算
+#testing the exit status
+var1=10
+var2=20
+var3=$[ $var1 + $var2]
+echo The answer is $var3
+exit 5
+

基本脚本/使用expr执行数学运算.sh

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+#!/bin/bash
+#An example of using the expr command
+
+var1=10
+var2=20
+var3=`expr $var2 / $var1`
+echo "The result is $var3"
+

基本脚本/使用内联重定向计算表达式.sh

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+#!/bin/bash
+
+var1=10.45
+var2=43.67
+var3=33.2
+var4=71
+
+var5=`bc <<EOF
+scale=4
+a1 = $var1 * $var2
+b1 = $var3 * $var4
+a1 + b1
+EOF
+`
+echo The final answer for this mess is $var5

基本脚本/使用方括号执行数学运算.sh

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+#!/bin/bash
+
+var1=10
+var2=50
+var3=45
+var4=$[$var1 * ($var2 - $var3)]
+echo 'The final result is '$var4

基本脚本/使用自定义变量.sh

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+#!/bin/bash
+#testing variables
+
+days=10
+guest="Katie"
+echo "$guest logged in $days days age"
+guest="Katie2"
+days=5
+echo "$guest logged in $days days age"

基本脚本/反引号的使用.sh

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+#!/bin/bash
+#using the backtick character
+
+testing=`date`
+echo "The date and time are:$testing"

基本脚本/在脚本中使用bc.sh

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+#!/bin/bash
+var1=100
+var2=45
+var3=`echo "scale=4; $var1 / $var2" | bc`
+echo The answer for this is $var3
+

基本脚本/显示时间和登录者.sh

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+#!/bin/bash
+#This script displays the date and who's logged on
+
+#如果想在同一行显示
+#echo -n -e 'The time is:\n\n'
+echo The time is:
+date
+echo The one who has been logged is:
+who
+
+
+

基本脚本/显示系统变量和转义字符.sh

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+#!/bin/bash
+#display user information from system
+
+echo "User info fro userId:$USER"
+echo UID:$UID
+echo HOME:$HOME
+#换行
+echo -e '\n'      
+echo 'The cost of the item is \$15'
+

基本脚本/通过反引号获得当前日期并生成唯一文件名.sh

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+#!/bin/bash
+#copy the /usr/bin directory listing to a log file
+
+today=`date +%y%m%d`
+ls /usr/bin -al > log.$today

处理用户输入/从文件中读取数据.sh

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+#!/bin/bash
+# reading data from a file
+
+count=1
+cat test | while read line
+do
+	echo "Line $count: $line"
+	count=$[ $count + 1 ]
+done
+echo "Finished processing the file"
+

处理用户输入/使用getopts.sh

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+#!/bin/bash
+# simple demonstration of the getopts command
+
+while getopts :ab:c opt
+do
+	case "$opt" in
+	a) echo "Found the -a option";;
+	b) echo "Found the -b option, with value $OPTARG";;
+	c) echo "Found the -c option";;
+	*) echo "Unknown option:$opt";;
+	esac
+done

处理用户输入/使用getopts处理选项和参数.sh

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+#!/bin/bash
+# processing options and parameters with getopts
+
+while getopts :ab:cd opt
+do
+	case "$opt" in
+	a) echo "Found the -a option";;
+	b) echo "Found the -b option,with value $OPTARG";;
+	c) echo "Found the -c option";;
+	d) echo "Found the -d option";;
+	*) echo "Unknown option: $opt";;
+	esac
+done
+shift $[ $OPTIND - 1 ]
+count=1
+for param in "$@"
+do
+	echo "Parameter $count: $param"
+	count=$[ $count + 1 ]
+done

处理用户输入/使用getopt命令.sh

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+#!/bin/bash
+#extracting command line options and values with getopt
+# getopt command is not goot at dealing with space,we can use getopts
+set -- `getopt -q ab:c "$@"`
+while [ -n "$1" ]
+do
+	case "$1" in
+	-a) echo "Found the -a option";;
+	-b) param="$2"
+		echo "Found the -b option,with parameter value $param"
+		shift;;
+	-c) echo "Found the -c option";;
+	--) shift
+		break;;
+	*) echo "$1 is not an option";;
+	esac
+	shift
+done
+
+count=1
+for param in "$@"
+do
+	echo "Parameter #$count: $param"
+	count=$[ $count+1 ]
+done

处理用户输入/使用shift命令.sh

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+#!/bin/bash
+# shift n 移动变量
+
+count=1
+while [ -n "$1" ]
+do
+	echo "Parameter #$count = $1"
+	count=$[ $count+1 ]
+	shift
+done
+
+echo -e "\n"
+
+# demonstrating a multi-position shift
+echo "The original parameters : $*"
+shift 2
+echo "Here's the new first parameter: $1"

处理用户输入/分离参数和选项.sh

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+#!/bin/bash
+
+#extracting options and parameters
+
+while [ -n "$1" ]
+do
+	case "$1" in 
+	-a) echo "Found the -a option";;
+	-b) echo "Found the -b option";;
+	-c) echo "Found the -c option";;
+	--) shift
+		break;;
+	*) echo "$1 is not an option";;
+	esac
+	shift
+done
+
+count=1
+for param in $@
+do
+	echo "Parameter #$count: $param"
+	count=$[ $count + 1 ]
+done

处理用户输入/参数计数.sh

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+#!/bin/bash
+# getting the number of parameters
+
+echo There were $# parameters supplied
+
+#花括号里不能使用美元符号
+params=$#
+
+echo The last parameter is $params
+echo The last parameter is ${!#}

处理用户输入/处理带值的选项.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+# extracting command line options and values
+
+while [ -n "$1" ]
+do 
+	case "$1" in
+	-a) echo "Found the -a option";;
+	-b) param="$2"
+		echo "Found the -b option, with parameter value $param"
+		shift;;
+	-c) echo "Found the -c option";;
+	--) shift
+		break;;
+	*) echo "$1 is not an option";;
+	esac
+	shift
+done
+
+count=1
+for param in "$@"
+do
+	echo "Parameter #$count : $param"
+	count=$[ $count + 1 ]
+done

处理用户输入/处理简单选项.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+# extracting command line options as parameters
+
+while [ -n "$1" ]
+do
+	case "$1" in
+	-a) echo "Found the -a option";;
+	-b) echo "Found the -b optins";;
+	-c) echo "Found the -c optins";;
+	*) echo "$1 is not a valid options";;
+	esac
+	shift
+done

处理用户输入/抓取所有数据.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+# testing $* and $@
+
+count=1
+for param in "$*"
+do
+	echo "\$* Parameter #$count = $param"
+	count=$[ $count+1 ]
+done
+
+count=1
+for param in "$@"
+do
+	echo "\$@ Paramenter #$count = $param"
+	count=$[ $count+1 ]
+done

处理用户输入/获取用户输入.sh

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+#!/bin/bash
+
+# testing the reading command
+
+echo -n "Enter your name:"
+read name
+echo "Hello $name, welcome to my program"
+
+read -p "Please enter your age: " age
+days=$[ $age * 365 ]
+echo "That makes you over $days days old"
+
+#指定多个变量，输入的每个数据值都会分配给表中的下一个变量，如果用完了，就全分配各最后一个变量
+read -p "Please enter name:" first last
+echo "Checking data for $last. $first..."
+
+#如果不指定变量，read命令就会把它收到的任何数据都放到特殊环境变量REPLY中
+read -p "Enter a number:"
+factorial=1
+for (( count=1; count<=$REPLY; count++))
+do
+	factorial=$[ $factorial * $count ]
+done
+echo "The factorial of $REPLY is $factorial"
+
+
+

处理用户输入/读取参数.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+# using one command line parameter
+
+factorial=1
+for (( number = 1; number <= $1; number++))
+do
+	factorial=$[ $factorial * $number ]
+done
+echo The factor of $1 is $factorial

处理用户输入/读取多个命令行参数.sh

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+#!/bin/bash
+
+# handing lots of parameters
+
+total=$[ ${10} * ${11} ]
+echo The tenth parameter is ${10}
+echo The eleventh parameter is ${11}
+echo The total is $total

处理用户输入/读取程序名.sh

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+#!/bin/bash
+# testing the $0 parameter
+
+echo The command entered is $0
+
+#当传给$0变量的真实字符串是整个脚本的路径是，程序中就会使用整个路径，而不仅仅是程序名
+
+name=`basename $0`
+echo The command entered is $name

处理用户输入/超时和输入计数.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+# timing the data entry
+
+if read -t 5 -p "Please enter your name:" name
+then
+	echo "Hello, $name, welcome to my script"
+else
+	#起到换行的作用
+	echo
+	#输入计数 -n1
+	read -n1 -p "Do you want to continue [Y/N]?" answer
+	case $answer in
+	Y | y) echo
+		   echo "Fine, continue on...";;
+	N | n) echo
+		   echo "OK，goodbye";;
+	*) echo
+	   echo "OK, wrong, goodbye"
+	esac
+	echo "Sorry, this is the end of the script"
+fi
+

处理用户输入/隐藏方式读取数据.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+# hiding input data from monitor
+
+read -s -p "Please enter your password: " pass
+
+#添加了-s选项之后，不会自动换行，不添加-s 会自动换行
+echo 
+echo "Is your password really $pass?"

理解输入和输出/2.sh

@@ -0,0 +1 @@
+#!/bin/bash

理解输入和输出/3.sh

@@ -0,0 +1 @@
+#!/bin/bash

理解输入和输出/4.sh

@@ -0,0 +1 @@
+#!/bin/bash

理解输入和输出/newsh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+#创建10个sh
+
+for (( i=1; i<=4; i++))
+do
+	touch $i.sh
+	echo '#!/bin/bash' > $i.sh
+	chmod 764 $i.sh
+done

理解输入和输出/test

@@ -0,0 +1,2 @@
+ls: cannot access badtest: No such file or directory
+but this should go to the testerror file

理解输入和输出/test1

@@ -0,0 +1 @@
+This is the end of the script

理解输入和输出/临时重定向.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+# testing STDERR messages
+
+echo "This is an error " >&2
+echo "This is another error"
+echo "This is also an error" >&2

理解输入和输出/在脚本中使用重定向输入.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+# redirecting the inpiut
+
+# 从test中读取数据，而不是从STDIN中读取数据
+exec 0< test
+count=1
+while read line
+do
+	echo "Line #$count : $line "
+	count=$[ $count +1 ]
+done
+

理解输入和输出/永久重定向.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+# testing STDERR messages
+# redirecting all to a file
+
+# 脚本执行期间，用exec命令告诉shell重定向某个特定文件描述符
+exec 2>test
+
+ls badtest
+echo "This is test of redirecting all output"
+echo "from a script to another file"
+
+exec 1>test1
+echo "This is the end of the script"
+echo "but this should go to the testerror file" >&2

结构化命令/bash-shell无法处理浮点数.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+#bash shell 仅能处理浮点数值,test命令无法处理val1变量中存储的浮点值
+
+#testing floating point numbers 
+
+val1=`echo "scale=4; 10 / 3" | bc`
+echo "The test value is $val1"
+if [ $val1 -gt 3 ]
+then
+	echo "The result is larger than 3"
+fi

结构化命令/continue退出多层循环.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+#continuing an outer loop
+
+for (( a=1; a<=5; a++))
+do
+	echo "Iteration $a:"
+	for (( b=1; b<3; b++ ))
+	do
+		if [ $a -gt 2 ] && [ $a -lt 4 ]
+		then	
+			continue 2
+		fi
+		var3=$[ $a * $b ]
+		echo " The result of $a * $b is $var3"
+	done
+done

结构化命令/if-then-else语句.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+#testing the else section
+testuser=badtest
+if grep $testuser /etc/passwd
+then
+	echo The files for user $testuser are:
+	ls -a /home/.b*
+else
+	echo "The user name $testuser does not exist on this system"
+fi

结构化命令/if-then语句.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+#testing the if statement
+if date
+then 
+	echo "it worked"
+fi
+echo -e '\n'
+if asd
+then 
+	echo "it not worked"
+fi
+echo 'We are outside the if statement'

结构化命令/output.txt

@@ -0,0 +1,12 @@
+/home/tiandi/Desktop is a directory
+/home/tiandi/Documents is a directory
+/home/tiandi/Downloads is a directory
+/home/tiandi/examples.desktop is a file
+/home/tiandi/lamp is a directory
+/home/tiandi/Music is a directory
+/home/tiandi/Pictures is a directory
+/home/tiandi/Public is a directory
+/home/tiandi/sh is a directory
+/home/tiandi/Templates is a directory
+/home/tiandi/test is a directory
+/home/tiandi/Videos is a directory

结构化命令/while里面嵌套for循环.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+# placing a for loop inside a while loop
+
+var1=5
+
+while [ $var1 -ge 0 ]
+do
+	echo "Outer loop: $var1"
+	for (( var2=1; $var2 < 3; var2++))
+	do
+		var3=$[ $var1*$var2]
+		echo "Inner loop: $var1 * $var2 = $var3"
+	done
+	var1=$[ $var1 - 1 ]
+done

结构化命令/两个for嵌套循环.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+#nesting for loops
+
+for (( a=1; a<=3; a++ ))
+do
+	echo "Starting loop $a:"
+	for (( b=1; b<=3; b++))
+	do
+		echo "Inside loog: $b:"
+	done
+done

结构化命令/从变量读取列表.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+# using a variable to hold the list
+
+list="Alabama Alaska Arizona"
+list=$list" Connecticut"
+
+for state in $list
+do
+	echo "Have you ever visited $state"
+done
+

结构化命令/从命令读取值.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+#reading values from a file
+
+file="state"
+
+#更改字段分隔符，使其只能识别换行符
+IFS=$'\n'
+
+#处理长脚本是，在一个地方修改了该值，然后可能忘了修改过该值
+#IFS.OLD=$IFS
+#IFS=$'\n'
+#具体代码
+#IFS=$IFS.OLD
+
+for state in `cat $file`
+do
+	echo "Visit beautiful $state"
+done

结构化命令/使用C语言风格的for命令.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+#testing the C-style for loop
+
+for (( i=1; i<=10; i++ ))
+do
+	echo "The next number is $i"
+done

结构化命令/使用break跳出外部循环.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+# break n，默认为1
+
+for (( a=1; a<=3; a++ ))
+do
+	echo "Outer loop : $a"
+	for (( b=1; b < 100; b++ ))
+	do 
+		if [ $b -gt 4 ]
+		then
+			break 2
+		fi
+		echo " Inner loop:$b"
+	done
+done
+

结构化命令/使用case语句.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+#using the case command
+
+case $USER in
+tiandi | barbar)
+	echo "Welcome, $USER"
+	echo "Pleas enjoy your visit";;
+testing)
+	echo "Special testing account";;
+jessica)
+	echo "Do not forget to logout when you are out";;
+*)
+	echo "Sorry, you are not allowed here";;
+esac

结构化命令/使用continue命令.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+#using the continue command
+
+for (( var1 = 1; var1 < 15; var1++ ))
+do
+	if [ $var1 -gt 5 ] && [ $var1 -lt 10 ]
+	then
+		continue
+	fi
+	echo "Iteration number:$var1"
+done

结构化命令/使用elif.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+# looking for a possible value
+
+if [ $USER = "tiandi" ]
+then 
+	echo "Welcome $USER"
+	echo "Please enjoy your visit"
+elif [ $USER = testing ]
+then
+	echo "Welcome $USER"
+	echo "Please enjoy your visit"
+elif [ $USER = barbar ]
+then
+	echo "Do not forget to logout when you're done"
+else
+	echo "Sorry, you are not allowed here"
+fi
+

结构化命令/使用test进行数值比较.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+var1=10
+var2=5
+if [ $var1 -gt 5 ]
+then
+	echo "The test value $var1 is greater than 5"
+fi
+if [ $var1 -eq $var2 ]
+then
+	echo "The values is equal"
+else
+	echo "The values are different"
+fi
+
+

结构化命令/使用until命令.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+
+#using the until command
+
+var1=100
+until [ $var1 -eq 0 ]
+do 
+	echo $var1
+	var1=$[ $var1-25 ]
+done
+
+var1=100
+until echo $var1
+	[ $var1 -eq 0 ]
+do
+	echo Inside the loop: $var1
+	var1=$[ $var1 - 25 ]
+done
+	
+	
+

结构化命令/使用while.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+# while command test
+ var1=10
+ while [ $var1 -gt 0 ]
+ do 
+	echo $var1
+	var1=$[ $var1 - 1 ]
+done
+

结构化命令/使用while多个测试命令.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+#testing a multicommand while loop
+
+var1=10
+while echo $var1
+	[ $var1 -ge 0 ]
+do	
+	echo 'This is inside the loop'
+	var1=$[ $var1 - 1 ]
+done

结构化命令/使用双圆括号.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+# using double parenthesis
+
+var1=10
+
+if (( $var1 ** 2 > 90))
+then 
+	(( var2 = $var1 ** 2))
+	echo "The square of $var1 if $var2"
+fi
+

结构化命令/使用双引号圈起用空格分隔的字符串.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+# another example of how not to use the for command
+
+for test in Newada "New Hampshire"
+do
+	echo "Now going to $test"
+done

结构化命令/使用双方括号.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+# using pattern matching
+
+if [[ $USER == r* ]]
+then 
+	echo "Hello $USER"
+else
+	echo "Sorry, I do not know you"
+fi

结构化命令/使用嵌套循环并修改IFS.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+#changing the IFS value
+
+IFS.OLD=$IFS
+IFS=$'\n'
+for entry in `cat /etc/passwd`
+do	
+	echo "Values in $entry -"
+	IFS=:
+	for value in $entry
+	do
+		echo " $value"
+	done
+done

结构化命令/使用符合条件测试.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+#testing compound comparisons
+
+if [ -d $HOME ] && [ -w $HOME/testing ]
+then
+	echo "The file exists and you can write to it"
+else
+	echo "I cannot write to it"
+fi

结构化命令/使用管道或重定向.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+
+# redirecting the for output to a file
+for file in /home/tiandi/*
+do
+	if [ -d "$file" ]
+	then
+		echo "$file is a directory"
+	else
+		echo "$file is a file"
+	fi
+done > output.txt
+
+# piping a loop to another command
+
+for state in "North Dakota" Connecticut
+do
+	echo "$state is next place to go"
+done | sort
+echo "This completes our travels"

结构化命令/使用通配符处理目录.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+#iterate through all the files in a directory
+for file in /home/tiandi/test/*
+do
+	if [ -d "$file" ]
+	then
+		echo "$file is a directory"
+	elif [ -f "$file" ]
+	then
+		echo "$file is a file"
+	fi
+done

结构化命令/判断字符串长度是否为零.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+# testing string length
+
+#-n 判断长度是否非零
+#-z 判断长度是否为零
+
+val1=testing
+val2=''
+
+if [ -n "$val1" ]
+then 
+	echo "The string $val1 is not empty"
+else
+	echo "The string $val1 is empty"
+fi
+
+if [ -z "$val2" ]
+then 
+	echo "The string $val2 is empty"
+else
+	echo "The string $val2 is not empty"
+fi
+if [ -z "$val3" ]
+then 
+	echo "The string $val3 is empty"
+else
+	echo "The string $val3 is not empty"
+fi
+

结构化命令/在for语句中使用多个变量.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+# multiple variables
+
+for (( a=1, b=10; a<=10; a++,b-- ))
+do
+	echo "$a - $b"
+done

结构化命令/在then块中使用多条命令.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+#testing multiple commands in the then section
+testuser=tiandi
+if grep $testuser /etc/passwd
+then
+	echo The bash files from user $testuser are:
+	ls -a /home/$testuser/.b*
+fi

结构化命令/字符串比较.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+#testing string equality
+
+testuser=tiandi
+
+if [ $USER = $testuser ]
+then
+	echo "Welcome $testuser"
+fi

结构化命令/嵌套if.sh

@@ -0,0 +1,2 @@
+#!/bin/bash
+

结构化命令/检查文件或目录是否存在.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# checking if a directory or a file exists
+
+if [ -e $HOME ]
+then
+	echo "OK on the directory.now to check the file"
+	#checking if a file exists
+	if [ -e $HOME/testing ]
+	then
+		#the file exists,append data to it
+		echo "Appending date to existing file"
+		date >> $HOME/testing
+	else
+		#the file is not exists,create a new file
+		echo "Creating a new file"
+		date > $HOME/testing
+	fi
+else
+	echo 'Sorry. you do not have a $HOME directory'
+fi

结构化命令/检查目录.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+# look before you leap
+
+if [ -d $HOME ]
+then
+	echo "Your home directory exists"
+	cd $HOME
+	ls -a
+else
+	echo "There is a problem with your HOME direcotry"
+fi

结构化命令/正确使用大于小于号.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+#正确使用大于小于号
+
+val1=baseball
+val2=hocky
+
+if [ $val1 \> $val2 ]
+then 
+	echo "$val1 is greater than $val2"
+else
+	echo "$val1 is less than $val2"
+fi

结构化命令/注意test大小写顺序和sort不同.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+#test命令中，大小字母会被当成小于小写字符，而在sort中，小写字母会先出现,test使用标准的ASCII排序，sort使用本地化语言设置进行排序，对于英语，本地化设置制定了排序顺序中小写字母出现在大写字母之前
+
+var1=Testing
+var2=testing
+
+if [ $val1 \> $val2 ]
+then
+	echo '$val1 is greater than $val2'
+else
+	echo '$val1 is less than $val2'
+fi

结构化命令/解决读取列表中的复杂值.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+for test in I don\'t know if "this'll" work
+do 
+	echo "word:$test"
+done

结构化命令/读取列表中的值.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# basic for command
+for test in Alabama Alaska Arizona
+do
+	echo The next state is $test
+done

结构化命令/读取里表中复杂的值.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+
+# another example of how not to use the for command
+
+for test in I don't know if this'll work
+do 
+	echo "word:$test"
+done

结构化命令/错误的使用大于小于号.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+# 大于小于号必须转义，否则shell会将它们当做重定向符号而把字符串值当做文件名处理
+# 大于小于号顺序和sort命令所采用的有所不同
+# mis-using string comparisons
+
+val1=baseball
+val2=hockey
+
+if [ $val1 > $val2 ]
+then
+	echo "$val1 is greater than $val2"
+else
+	echo "$val1 is less than $val2"
+fi