shell小结(8)

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内建命令，即bash内置的命令

#!/bin/bash

cd()
{
	echo 'ok'
}

cd

echo 'now buitin'

builtin cd

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echo ${UID}_
It is safe to omit the curly brackets ({}) if the variable name is followed by a character 
that isn't a letter, digit, or underscore. 


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排序命令：将当前目录按从大到小排序
du -s * | sort -nr

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ls命令：
ls -1：很重要，这个数字1，看下面的实用例子
CLASSPATH=`ls -1 $WAD_HOME/shared/lib/*.jar|/usr/bin/tr '\n' ':'`$CLASSPATH; export CLASSPATH

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AIC2 ftp1204/.dd> cat book5.sh
#!/bin/bash

####这仅仅是在脚本中改变!!!###
cd ../.. 

echo `ls -l`

ls -S:大小排序

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yes --help 
用法：yes [字符串]... 
　或：yes 选项 
重复输出一行指定的字符串，或者重复输出"y"。 

      --help 显示此帮助信息并退出 
      --version 显示版本信息并退出 



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select 语法 ：

select 表达式是一种bash的扩展应用，尤其擅长于交互式使用。用户可以从一组不同的值中进行选择。

经常与case使用

#!/bin/bash

#设置提示信息，PS3就是这个作用
PS3="choose your favorate food:"
select i in "apple" "orange" "banana"
do
	case $i in
	"apple")
		echo "your choosed apple"
		;;
	"orange")
		echo "you choosed orange"
		;;
	"banana")
		echo "you choosed banana"
		;;
	*)
		echo "you have other choice"
	esac
	#必须要有退出语句
	break;
done

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########下面这种方式是等价的##########
ftp1204@AIC2:~/.dd> echo 'abc' | sed -e 's/a/A/g'
Abc
ftp1204@AIC2:~/.dd> echo 'abc' | sed -e 's:a:A:g'
Abc

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