Bash shell基础

#! /bin/bash    #解析器路径
env                     #查看环境

#!/bin/bash
#文件名: time.sh
start=$(date +%s)
#commands;
#statements;
sleep 10;               #command 
end=$(date +%s)
difference=$(( end - start))
echo Time taken to execute $0 is $difference seconds.

#!/bin/bash
declare -i i=1
declare -i sum=0
while ((i<=10))
do
      let sum+=i
      let ++i
done
echo $sum

#!/bin/bash
#文件名: sleep.sh
echo -n Count:
# tput sc存储光标位置
tput sc
count=0;
while true;
do
    if [ $count -lt 40 ];
    then
        let count++;
        sleep 1;
        # 恢复光标位置的命令是tput rc
        tput rc
        # tput ed清除从当前光标位置到行尾之间的所有内容 
        tput ed
        echo -n $count;
    else exit 0;
    fi
done

#! /bin/bash
declare -i num=0
if [ $num -lt 0 ] #一定要注意在[或]与操作数之间有一个空格
then
    echo "<";
elif [ $num -eq 0 ]
then
    echo "==";
else
    echo ">";
fi
#   [ $var1 -ne 0 -a $var2 -gt 2 ] #使用逻辑与-a
#   [ $var1 -ne 0 -o var2 -gt 2 ] #逻辑或 -o

#!/bin/bash
#文件名: debug.sh
for i in {1..6};
do
    set -x
    echo $i
    set +x
done
echo "Script executed"

#!/bin/bash
while :
do
    echo -n "Input a number between 1 to 5: "
    read aNum
    case $aNum in
        1|2|3|4|5) echo "Your number is $aNum!"
                    ;;
        *) echo "You do not select a number between 1 to 5, game is over!"
            break
            ;;
    esac
done

#! /bin/bash
echo ‘Input a number between 1 to 4‘
echo ‘Your number is:\c‘
read aNum
case $aNum in
     1)  echo ‘You select 1‘
             ;;
     2)  echo ‘You select 2‘
             ;;
     3)  echo ‘You select 3‘
             ;;
     4)  echo ‘You select 4‘
             ;;
     *)  echo ‘You do not select a number between 1 to 4‘
             ;;
esac

function fname()
{
    echo $1, $2; #访问参数1和参数2
    echo "$@";#以列表的方式一次性打印所有参数
    echo "$*"; #类似于$@，但是参数被作为单个实体
    return 0; #返回值
}

fname arg1 arg2 arg3

export -f fname