1.linux系统下shell脚本用ca语句编写四则运算 2.linux系统下shell脚本输入数字串。进行反序输出
原来我拿shell写的计算器：
[root@liuxiting testdir]# cat calculator.sh
#!/bin/bash
echo "usage: 1+3 <Enter> ,q <Enter> is quit"
while [ 1 ]
do
read -p "->>" str 1>>/dev/null
a=`echo $str |awk -F '+|-|*|/' '{print $1}'`
if [ $a == q ]
then
break
fi
b=`echo $str |awk -F '+|-|*|/' '{print $2}'`
o=`echo $str |grep -o "[[:punct:]]" | grep -v "\."`
ca $o in
+) awk 'BEGIN{printf " =%.2f\n",'$a'+'$b'}';;
-) awk 'BEGIN{printf " =%.2f\n",'$a'-'$b'}';;
\*) awk 'BEGIN{printf " =%.2f\n",'$a'*'$b'}';;
/)if [ $b -eq 0 ]
then
echo 0 Can NOT be denominator!
continue
fi
awk 'BEGIN{printf " =%.2f\n",'$a'/'$b'}';;
#^) awk 'BEGIN{printf " =%.2f\n",'$a'**'$b'}';;
*) echo error;;
esac
done
刚刚写的倒序输出：
[root@liuxiting testdir]# cat daoXuShuChu.sh
#!/bin/bash
echo "usage: 123456 <Enter>, q <Enter> is quit"
while [ 1 ]
do
echo -n "Pleasw enter number : "
read n
if [ $n == 'q' ]
then
break
fi
sd=0
rev=""
on=$n
echo "$n"
while [ $n -gt 0 ]
do
sd=$(( $n % 10 )) # get Remainder
n=$(( $n / 10 )) # get next digit
rev=$( echo $rev$sd)
done
echo "$on in a rever order $rev"
done
用shell做个加减乘除运算
看到真有点疑惑，不是做加法怎么去做减法了。其次t是设置shell变量吧。
还有前两个参数不是数字，最后一个是运算符么？怎么还去测试第三个参数和第一个参数相等。
以下是根据你例子修改的（没检查位置参数不全，不正确这类异常情况。）
#!/bin/bash
exportd=0
if["$3"-eq"+"]
then
echo$3
d=$(($1+$2))
fi
echo$d
shell 脚本里面从一个文本里面读出一个数字，如何转换成整数？我需要用这个数字进行加减乘除
可以参考下面几种方法：
法一：
echo ${var%.*} #这个是直接去除小数点及后面所有内容，只用于bash
法二：
echo $var | awk -F. '{print $1}' #以小数点为分隔符取第一个字段
法三：
echo $var | awk '{print int($0)}' #awk中可直接使用C函数取整
扩展资料：
shell脚本
shell script是利用shell的功能所写的一个程序，这个程序是使用纯文本文件，将一些shell的语法与指令写在里面，然后用正规表示法，管道命令以及数据流重导向等功能，以达到我们所想要的处理目的。
更明白地来说，shell script就像早期dos年代的.bat，最简单的功能就是将许多指令汇整写一起，让使用者很容易地就能够一个操作执行多个命令。
参考资料来源：百度百科-Shell脚本
在Linux下，用shell编写一个简单的计算器，要实现加减乘除4个功能就行了
不用写吧，本来有个 bc 命令可用，没有下载就成.
非要写一个，zsh 的function里有一个，名 zcalc,
贴上来给你
#!/usr/bin/zsh -i
#
# Zsh calculator. Understands most ordinary arithmetic expressions.
# Line editing and history are available. A blank line or `q' quits.
#
# Runs as a script or a function. If ud as a function, the history
# is remembered for reu in a later call (and also currently in the
# shell's own history). There are various problems using this as a
# script, so a function is recommended.
#
# The prompt shows a number for the current line. The corresponding
# result can be referred to with $<line-no>, e.g.
# 1> 32 + 10
# 42
# 2> $1 ** 2
# 1764
# The t of remembered numbers is primed with anything given on the
# command line. For example,
# zcalc '2 * 16'
# 1> 32 # printed by function
# 2> $1 + 2 # typed by ur
# 34
# 3>
# Here, 32 is stored as $1. This works in the obvious way for any
# number of arguments.
#
# If the mathfunc library is available, probably understands most system
# mathematical functions. The left parenthesis must be adjacent to the
# end of the function name, to distinguish from shell parameters
# (translation: to prevent the maintainers from having to write proper
# lookahead parsing). For example,
# 1> sqrt(2)
# 1.4142135623730951
# is right, but `sqrt (2)' will give you an error.
#
# You can do things with parameters like
# 1> pi = 4.0 * atan(1)
# too. The go into global parameters, so be careful. You can declare
# local variables, however:
# 1> local pi
# but note this can't appear on the same line as a calculation. Don't
# u the variables listed in the `local' and `integer' lines below
# (translation: I can't be bothered to provide a sandbox).
#
# Some constants are already available: (ca nsitive as always):
# PI pi, i.e. 3.1415926545897931
# E e, i.e. 2.7182818284590455
#
# You can also change the output ba.
# 1> [#16]
# 1>
# Changes the default output to hexadecimal with numbers preceded by `16#'.
# Note the line isn't remembered.
# 2> [##16]
# 2>
# Change the default output ba to hexadecimal with no prefix.
# 3> [#]
# Ret the default output ba.
#
# This is bad on the builtin feature that you can change the output ba
# of a given expression. For example,
# 1> [##16] 32 + 20 / 2
# 2A
# 2>
# prints the result of the calculation in hexadecimal.
#
# You can't change the default input ba, but the shell allows any small
# integer as a ba:
# 1> 2#1111
# 15
# 2> [##13] 13#6 * 13#9
# 42
# and the standard C-like notation with a leading 0x for hexadecimal is
# also understood. However, leading 0 for octal is not understood --- it's
# too confusing in a calculator. U 8#777 etc.
#
# Options: -#<ba> is the same as a line containing just `[#<ba>],
# similarly -##<ba>; they t the default output ba, with and without
# a ba discriminator in front, respectively.
#
#
# To do:
# - parate zcalc history from shell history using arrays --- or allow
# zsh to switch internally to and from array-bad history.
emulate -L zsh
topt extendedglob
local line ans ba defba forms match mbegin mend psvar optlist opt arg
local compcontext="-math-"
integer num outdigits outform=1
# We u our own history file with an automatic pop on exit.
history -ap "${ZDOTDIR:-$HOME}/.zcalc_history"
forms=( '%2$g' '%.*g' '%.*f' '%.*E' )
zmodload -i zsh/mathfunc 2>/dev/null
: ${ZCALCPROMPT="%1v> "}
# Supply some constants.
float PI E
(( PI = 4 * atan(1), E = exp(1) ))
# Process command line
while [[ -n $1 && $1 = -(|[#-]*) ]]; do
optlist=${1[2,-1]}
shift
[[ $optlist = (|-) ]] && break
while [[ -n $optlist ]]; do
opt=${optlist[1]}
optlist=${optlist[2,-1]}
ca $opt in
('#') # Default ba
if [[ -n $optlist ]]; then
arg=$optlist
optlist=
elif [[ -n $1 ]]; then
arg=$1
shift
el
print "-# requires an argument" >&2
return 1
fi
if [[ $arg != (|\#)[[:digit:]]## ]]; then
print - "-# requires a decimal number as an argument" >&2
return 1
fi
defba="[#${arg}]"
;;
esac
done
done
for (( num = 1; num <= $#; num++ )); do
# Make sure all arguments have been evaluated.
# The `$' before the cond argv forces string rather than numeric
# substitution.
(( argv[$num] = $argv[$num] ))
print "$num> $argv[$num]"
done
psvar[1]=$num
while vared -cehp "${(%)ZCALCPROMPT}" line; do
[[ -z $line ]] && break
# special cas
# Set default ba if `[#16]' or `[##16]' etc. on its own.
# Unt it if `[#]' or `[##]'.
if [[ $line = (#b)[[:blank:]]#('[#'(\#|)(<->|)']')[[:blank:]]#(*) ]]; then
if [[ -z $match[4] ]]; then
if [[ -z $match[3] ]]; then
defba=
el
defba=$match[1]
fi
print -s -- $line
line=
continue
el
ba=$match[1]
fi
el
ba=$defba
fi
print -s -- $line
ca ${${line##[[:blank:]]#}%%[[:blank:]]#} in
q) # Exit if `q' on its own.
return 0
;;
norm) # restore output format to default
outform=1
;;
sci[[:blank:]]#(#b)(<->)(#B))
outdigits=$match[1]
outform=2
;;
fix[[:blank:]]#(#b)(<->)(#B))
outdigits=$match[1]
outform=3
;;
eng[[:blank:]]#(#b)(<->)(#B))
outdigits=$match[1]
outform=4
;;
local([[:blank:]]##*|))
eval $line
line=
continue
;;
*)
# Latest value is stored as a string, becau it might be floating
# point or integer --- we don't know till after the evaluation, and
# arrays always store scalars anyway.
#
# Since it's a string, we'd better make sure we know which
# ba it's in, so don't change that until we actually print it.
eval "ans=\$(( $line ))"
# on error $ans is not t; let ur re-edit line
[[ -n $ans ]] || continue
argv[num++]=$ans
psvar[1]=$num
;;
esac
if [[ -n $ba ]]; then
print -- $(( $ba $ans ))
elif [[ $ans = *.* ]] || (( outdigits )); then
printf "$forms[outform]\n" $outdigits $ans
el
printf "%d\n" $ans
fi
line=
done
return 0
支援小数点，+ - * / , ok
