linux学习day04（shell学习）

1. $#:传入脚本的命令行参数个数（和c的区别，c的个数包括命令本身）
2. $*:所有命令行参数值，在各个参数值间留有空格
3. $0;命令本身
4. $1:第一个命令行参数
5. $2:第二个命令行参数

#!/bin/bash
a=$1
b=$2
if [ -z $a ] || [ -z $b ]
then
    echo "please enter 2 no"
    exit 1
fi
if [ $a -eq $b ] ; then
    echo "number a = number b"
else if [ $a -gt $b ]
    then
        echo "number a>number b"
    elif [ $a -lt $b ]
        then
            echo "number a<number b"
    fi
fi

#!/bin/sh 
folder=/home 
[ -r "$folder" ] && echo "Can read $folder" 
[ -f "$folder" ] || echo "this is not file" 

#!/bin/bash 
for day in Sun Mon Tue Wed Thu Fri Sat
do
    echo $day
done 

统计当前目录下的文件数

#!/bin/bash

counter=0
for files in *
do
    counter=`expr $counter + 1`
done
echo "There are $counter files in `pwd` we need to process"

#!/bin/bash
echo -n "Pleasw enter number : "
read n
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 reverse order $rev"

#!/bin/bash
if [ "$1" = "" ] || [ "$2" = "" ]
then
    echo "Please enter file name"
    exit 1
fi
if [ -e $2 ]
then
    echo "The file already exists"
    until [ ! -f $2 ]
    do
        sleep 1
    done
fi
if [ ! `mv $1 $2` ]
then
    echo "mv sucessful"
else
    echo "mv error"
fi

#!/bin/bash 
echo "Hit a key, then hit return."
read Keypress 
case "$Keypress" in
    [A-Z] ) echo "Uppercase letter";;
    [a-z] ) echo "Lowercase letter";;
    [0-9] ) echo "Digit";;
    * ) echo "Punctuation, whitespace, or other";;
esac