Linux shell脚本编程基础之练习篇

　　shell脚本编程基础之练习篇。

• 1、编写一个脚本使我们在写一个脚本时自动生成”#!/bin/bash”这一行和注释信息。

#!/bin/bash
if [ $# -ne  ]
then
        echo "请输入一个参数"
        exit
else
        echo "参数正确"
        newfile=$
fi

#echo `grep "^#\!" ${newfile}`

if ! grep "^#\!" ${newfile} &>/dev/null
then
cat >>${newfile}<<EOF
#!/bin/bash
# Author: Inert Your Name here.
#Date & Time: `date +"%F %T"`
#Description: Please Edit here.
EOF
fi
vi + ${newfile}

将脚本改个名字例如：newshfile，将其放置在/bin/目录下，那么你的系统就多了一个新的newshfile命令了

• 2、求100以内偶数的和

#!/bin/bash
# Author: Inert Your Name here.
#Date & Time: -- ::
#Description: Please Edit here.
let sum=
for index in {..}
do
if [ $[ ${index}% ] ==  ]; then
        #let sum+=${index}
        sum=`expr ${sum} + ${index}`
fi
done
echo "sum=${sum}"

let sum=
for num in $(seq  ); do
if [ $[ $num %  ] ==  ]; then
        sum=`expr $sum + $num`
fi
done
echo "sum=$sum"

• 判断输入的参数个数，如果为两个参数则相加并输出相加后的值

#!/bin/bash
if [ $# -eq  ]
then
        echo "参数个数 $#\n"
        echo "参数相加 $1 + $2 = `expr $1 + $2`"
else
        echo "参数个为 $#，本脚本需要两个参数"
fi

• 用while\for循环降序输出1~5的值

#!/bin/sh
num=
while test $num !=
do
        echo "$num"
        num=`expr $num - `
done

echo "*****************************"
num=
while (($num != ))
do
        echo "$num"
        num=`expr $num - `
done

echo "*****************************"
for num in {..}
do
        echo "$num"
done

echo "*****************************"
for ((num=;$num>;num=`expr $num - `))
do
        echo "$num"
done

• 加减乘除运算

#!/bin/bash
# Author: Inert Your Name here.
#Date & Time: -- ::
#Description: Please Edit here.
if test $# ==
then
        echo "参数个数$#，参数：$@"
case $ in
        +)
        num=`expr $ + $`
        ;;
        -)
        num=`expr $ - $`
        ;;
        x)
        num=`expr $ \* $`
        ;;
        /)
        num=`expr $ \/ $`
        ;;
        *)
        echo "只允许+ - x /这几个运算符"
        ;;
esac
echo "num=$num"
else
        echo "参数个数为3个，分别为\"运算符 参数1 参数2\""
fi

• 浮点数的运算

echo 5.12 + 2.5 | bc

#!/bin/bash
# Author: Inert Your Name here.
#Date & Time: -- ::
#Description: Please Edit here.

a=5.66
b=8.67
c=`echo $a + $b | bc`
echo "$a + $b = $c"

• 打印以下各种图形效果

****************************

****************************
|_
||_
|||_
||||_
|||||_
****************************
 *
 * *
 * * *
 * * * *
 * * * * *
 * * * * *
 * * * *
 * * *
 * *
 *
************lengxing****************
      *
     * *
    * * *
   * * * *
  * * * * *
 * * * * * *
  * * * * *
   * * * *
    * * *
     * *
      *

#!/bin/bash
# Author: Inert Your Name here.
#Date & Time: -- ::
#Description: Please Edit here.

for ((num=;$num<=;num=`expr $num + `))
do
        for((index=$num;$index>;index=`expr $index - `))
        do
                echo -n "$num"
        done
echo ""
done 

echo "****************************"
for ((num=;$num<=;num=`expr $num + `))
do
        for((index=;$index<=$num;index=`expr $index + `))
        do
                echo -n "$index"
        done
echo ""
done

echo "****************************"
for ((num=;$num<=;num=`expr $num + `))
do
        for((index=;$index<=$num;index=`expr $index + `))
        do
                if [ $index% ==  ]; then
                        echo -n " "
                else
                        echo -n "|"
                fi
        done
echo -n "_"
echo ""
done

echo "****************************"
for (( i=; i<=; i++ ))
do
    for (( j=; j<=i;  j++ ))
    do
     echo -n " *"
    done
    echo ""
done

for (( i=; i>=; i-- ))
do
    for (( j=; j<=i;  j++ ))
    do
     echo -n " *"
    done
    echo ""
done

echo "************lengxing****************"
max=
for ((i=; i<=$max; i++))
do
        for ((j=$max-i; j>; j--))
        do
                echo -n " "
        done
        for ((k=; k<=i; k++))
        do
                echo -n " *"
        done
        echo ""
done

for ((i=; i<=$max; i++))
do
        for ((k=; k<=i; k++))
        do
                echo -n " "
        done
        for ((j=$max-i; j>; j--))
        do
                echo -n " *"
        done
        echo ""
done