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#!/bin/sh
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# calc.sh -- 一个看起来像是bc的前端的命令行计算器
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scale=2
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show_help()
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{
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cat << EOF
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In addition to standard math function, calc also supports
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a % b remainder of a/b
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a ^ b exponential: a raised to the b power
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s(x) sine of x, x in radians
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c(x) cosine of x, x in radians
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a(x) actangent of x, returns radians
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l(x) natural log of x
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e(x) exponential log of raising e to the x
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j(n, x) bessel function of integer order n of x
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scale N show N fractional digits(default = 2)
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EOF
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}
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if [ $# -gt 0 ]; then
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exec scriptbc.sh "$@"
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fi
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echo "Calc - a simple calculator. Enter 'help' for help, 'quit' to quit."
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echo -n "calc> "
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while read command args # 像不像Python的顺序解包
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do
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case $command in
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quit|exit) exit 0;;
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help|\?) show_help;;
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scale) scale=$args;;
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*) scriptbc.sh -p $scale "$command" "$args";;
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esac
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echo -n "calc> "
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done
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echo ""
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exit 0
脚本如何运行：
可能这个脚本最有意思的部分就是那个while循环了，
交互式计算器脚本
，电脑资料
《交互式计算器脚本》(https://www.unjs.com)。它创建一个calc>的提示，直到用户完成输入。当然，这个脚本的间接性成就了它自己：shell脚本并不需要特别的复杂。运行脚本：
这个脚本跑起来非常简单，因为它是一个交互式的，可以提示用户完成特定操作。如果有参数传递给它，它就转而把这些参数传给scripbc.sh。
运行结果：
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calc 150 / 3.5
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42.85
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./calc.sh
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Calc - a simple calculator. Enter 'help' for help, 'quit' to quit.
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calc> help
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In addition to standard math function, calc also supports
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a % b remainder of a/b
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a ^ b exponential: a raised to the b power
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s(x) sine of x, x in radians
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c(x) cosine of x, x in radians
13
a(x) actangent of x, returns radians
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l(x) natural log of x
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e(x) exponential log of raising e to the x
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j(n, x) bessel function of integer order n of x
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scale N show N fractional digits(default = 2)
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calc> 54354 ^ 3
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160581137553864
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calc> quit