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/bashif [ $# -ne 1 ]then        echo "请输入一个参数"        exitelse        echo "参数正确"        newfile=$1fi#echo `grep "^#\!" ${newfile}`if ! grep "^#\!" ${newfile} &>/dev/nullthencat >>${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: 2015-06-02 20:37:07#Description: Please Edit here.let sum=0for index in {
   1..100}doif [ $[ ${index}%2 ] == 0 ]; then        #let sum+=${index}        sum=`expr ${
   sum} + ${index}`fidoneecho "sum=${sum}"let sum=0for num in $(seq 1 100); doif [ $[ $num % 2 ] == 0 ]; then        sum=`expr $sum + $num`fidoneecho "sum=$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/bashif [ $# -eq 2 ]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/shnum=5while test $num != 0do        echo "$num"        num=`expr $num - 1`doneecho "*****************************"num=5while (($num != 0))do        echo "$num"        num=`expr $num - 1`doneecho "*****************************"for num in {
   5..1}do        echo "$num"doneecho "*****************************"for ((num=5;$num>0;num=`expr $num - 1`))do        echo "$num"done

•  加减乘除运算

#!/bin/bash# Author: Inert Your Name here.#Date & Time: 2015-06-02 21:32:51#Description: Please Edit here.if test $# == 3then        echo "参数个数$#，参数：$@"case $1 in        +)        num=`expr $2 + $3`        ;;        -)        num=`expr $2 - $3`        ;;        x)        num=`expr $2 \* $3`        ;;        /)        num=`expr $2 \/ $3`        ;;        *)        echo "只允许+ - x /这几个运算符"        ;;esacecho "num=$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: 2015-06-02 22:07:28#Description: Please Edit here.a=5.66b=8.67c=`echo $a + $b | bc`echo "$a + $b = $c"

• 打印以下各种图形效果

122333444455555****************************112123123412345****************************|_||_|||_||||_|||||_**************************** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *************lengxing****************      *     * *    * * *   * * * *  * * * * * * * * * * *  * * * * *   * * * *    * * *     * *      *

#!/bin/bash# Author: Inert Your Name here.#Date & Time: 2015-06-02 22:24:41#Description: Please Edit here.for ((num=1;$num<=5;num=`expr $num + 1`))do        for((index=$num;$index>0;index=`expr $index - 1`))        do                echo -n "$num"        done echo ""done echo "****************************"for ((num=1;$num<=5;num=`expr $num + 1`))do        for((index=1;$index<=$num;index=`expr $index + 1`))        do                echo -n "$index"        doneecho ""doneecho "****************************"for ((num=1;$num<=5;num=`expr $num + 1`))do        for((index=1;$index<=$num;index=`expr $index + 1`))        do                if [ $index%2 == 0 ]; then                        echo -n " "                else                        echo -n "|"                fi        doneecho -n "_"echo ""doneecho "****************************"for (( i=1; i<=5; i++ ))do    for (( j=1; j<=i;  j++ ))    do     echo -n " *"    done    echo ""donefor (( i=5; i>=1; i-- ))do    for (( j=1; j<=i;  j++ ))    do     echo -n " *"    done    echo ""doneecho "************lengxing****************"max=6for ((i=1; i<=$max; i++))do        for ((j=$max-i; j>0; j--))        do                echo -n " "        done        for ((k=1; k<=i; k++))        do                echo -n " *"        done        echo ""donefor ((i=1; i<=$max; i++))do        for ((k=1; k<=i; k++))        do                echo -n " "        done        for ((j=$max-i; j>0; j--))        do                echo -n " *"        done        echo ""done