1...100的求和
非递归：
!/bin/bash
read num
count=1
sum=0
val=""
ret=""
while [ $count -le $num ]
do
if [ $count -eq $num ];then
val=$count
else
val=${count}'+'
fi
let sum+=count
let count++
ret=${ret}${val}
done
echo ${ret}'='$sum
递归：
!/bin/bash
read num
function add(){
local val=$1
local count=0
local sum=0
local num=$val
if [ $val -eq 1 ];then
echo 1
return
fi
arr=$count1+$val
let val--
let count=$( add $val )
let sum=$count+$num
echo $sum
}
ret=$(add $num)
echo $ret
结果：
[fbl@www test6_19]$ ./add.sh
100
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50+51+52+53+54+55+56+57+58+59+60+61+62+63+64+65+66+67+68+69+70+71+72+73+74+75+76+77+78+79+80+81+82+83+84+85+86+87+88+89+90+91+92+93+94+95+96+97+98+99+100=5050
求一个文件中数的最大最小值
!/bin/bash
read name
max=0
min=0
count=0
while read line
do
if [ $count -eq 1 ];then
min=$line
fi
(( count++ ))
if [ $max -lt $line ];then
max=$line
fi
if [ $min -gt $line ];then
min=$line
fi
done <$name
echo "max: "$max "min: "$min
斐波那契数列求和
非递归
!/bin/bash
read num
fib_val[0]=1
fib_val[1]=1
count=0
function fib(){
local val=$1
while [ $count -lt $val ]
do
let fib_val[${count}+2]=${fib_val[${count}+1]}+${fib_val[$count]}
let count++
done
}
fib $num
echo ${fib_val[$count]}
递归：
!/bin/bash
read num
function fib(){
local val=$1
local num1=0
local num2=0
if [ $val -eq 0 -o $val -eq 1 ];then
echo 1
return
fi
let val--
num1=$( fib $val )
let val--
num2=$( fib $val )
let sum=$num1+$num2
echo $sum
}
结果：
[fbl@www test6_19]$ ./fib.sh
1
1
[fbl@www test6_19]$ ./fib.sh
2
2
[fbl@www test6_19]$ ./fib.sh
11
144
字符串截取的应用
!/bin/bash
read name
str1=""
str2=""
str3=""
str=""
while read line
do
str1=$(echo $line|cut -c 1-3)
str2=$(echo $line|cut -c 4-6 |tr '[a-z]' '[A-Z]')
str3=$(echo $line|cut -c 7-9)
str="${str3}""${str2}""${str1}"
echo $str
done <$name >file_bak
结果：
[fbl@www test6_19]$ cat file1
123abc789
456def789
364rgy532
278bsy682
[fbl@www test6_19]$ vim string.sh
[fbl@www test6_19]$ ./string.sh
file1
[fbl@www test6_19]$ cat file_bak
789ABC123
789DEF456
532RGY364
682BSY278
