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?

# cd /usr/local/sbin/
# vim first.sh //加入如下內(nèi)容
#! /bin/bash
## This is my first shell script.
## Writen by Aming 2022-12-02.
date
echo "Hello world!"

# sh first.sh
Fri Dec  2 22:16:56 CST 2022
Hello world!

# ./first.sh
-bash: ./first.sh: 權(quán)限不夠
# chmod +x first.sh
# ./first.sh
Fri Dec  2 2256 CST 2022
Hello world!

# sh -x first.sh
+ date
Fri Dec  2?2243?CST?2022
+ echo 'Hello world!'
Hello world!

• date +%Y：表示以四位數(shù)字格式打印年份。
• ?
• date +%y：表示以?xún)晌粩?shù)字格式打印年份。
• ?
• date +%m：表示月份。
• ?
• date +%d：表示日期。
• ?
• date +%H：表示小時(shí)。
• ?
• date +%M：表示分鐘。
• ?
• date +%S：表示秒。
• ?
• date +%w：表示星期。結(jié)果顯示0則表示周日。 ? ?

# date +"%Y-%m-%d %H:%M:%S"
2022-12-02?2203

# date -d "-1 day" +%d
01

# date -d "-1 hour" +%H
21

# date -d "-1 min" +%M
17

# vim variable.sh
#! /bin/bash
## In this script we will use variables.
## Writen by Aming 2022-12-02.
d=`date +%H:%M:%S`
echo "The script begin at $d."
echo "Now we'll sleep 2 seconds."
sleep 2
d1=`date +%H:%M:%S`
echo "The script end at $d1."

# sh variable.sh
The script begin at 2204.
Now we'll sleep 2 seconds.
The script end at 2206.

# vim sum.sh
#! /bin/bash
## For get the sum of two numbers.
##?Aming?2022-12-02.
a=1
b=2
sum=$[$a+$b]
echo "$a+$b=$sum"

# sh sum.sh
1+2=3

# cat read.sh
#! /bin/bash
## Using 'read' in shell script.
## Aming 2022-12-02.
read -p "Please input a number: " x
read -p "Please input another number: " y
sum=$[$x+$y]
echo "The sum of the two numbers is: $sum"

# sh read.sh
Please input a number: 2
Please input another number: 10
The sum of the two numbers is: 12

# sh -x read.sh
+ read -p 'Please input a number: ' x
Please input a number: 22
+ read -p 'Please input another number: ' y
Please input another number: 13
+ sum=35
+ echo 'The sum of the two numbers is: 35'
The sum of the two numbers is: 35

# vim option.sh //內(nèi)容如下
#! /bin/bash
sum=$[$1+$2]
echo "sum=$sum"

# sh -x option.sh 1 2
+ sum=3
+ echo sum=3
sum=3

#! /bin/bash
echo "$1 $2 $0"

# sh option.sh 1 2
1 2 option.sh

if 判斷語(yǔ)句; then
command
fi

# cat if1.sh
#! /bin/bash
read -p "Please input your score: " a
if ((a<60)); then
echo "You didn't pass the exam."
fi

# sh if1.sh
Please input your score: 90
# sh if1.sh
Please input your score: 33
You didn't pass the exam.

if 判斷語(yǔ)句; then
command
else
command
fi

# vim if2.sh //內(nèi)容如下
#! /bin/bash
read -p "Please input your score: " a
if ((a<60)); then
echo "You didn't pass the exam."
else
echo "Good! You passed the exam."
fi

# sh if2.sh
Please input your score: 80
Good! You passed the exam.
# sh if2.sh
Please input your score: 25
You didn't pass the exam.

if 判斷語(yǔ)句1; then
command
elif 判斷語(yǔ)句2; then
command
else
command
fi

# vim if3.sh //內(nèi)容如下
#! /bin/bash
read -p "Please input your score: " a
if ((a<60)); then
echo "You didn't pass the exam."
elif ((a>=60)) && ((a<85)); then
echo "Good! You pass the exam."
else
echo "Very good! Your score is very high!"
fi

# sh if3.sh
Please input your score: 90
Very good! Your score is very high!
# sh if3.sh
Please input your score: 60
Good! You pass the exam.

# a=10; if [ $a -lt 5 ]; then echo ok; fi
# a=10; if [ $a -gt 5 ]; then echo ok; fi
ok
# a=10; if [ $a -ge 10 ]; then echo ok; fi
ok
# a=10; if [ $a -eq 10 ]; then echo ok; fi
ok
# a=10; if [ $a -ne 10 ]; then echo ok; fi

# a=10; if [ $a -lt 1 ] || [ $a -gt 5 ]; then echo ok; fi
ok
# a=10; if [ $a -gt 1 ] || [ $a -lt 10 ]; then echo ok; fi
ok

• -e：判斷文件或目錄是否存在。
• -d：判斷是不是目錄以及是否存在。
• -f：判斷是不是普通文件以及是否存在。
• -r：判斷是否有讀權(quán)限。
• -w：判斷是否有寫(xiě)權(quán)限。
• -x：判斷是否可執(zhí)行。 ? ?

if [ -e filename ] ; then
command
fi

# if [ -d /home/ ]; then echo ok; fi
ok
# if [ -f /home/ ]; then echo ok; fi

# if [ -f /root/test.txt ]; then echo ok; fi
ok
# if [ -r /root/test.txt ]; then echo ok; fi
ok
# if [ -w /root/test.txt ]; then echo ok; fi
ok
# if [ -x /root/test.txt ]; then echo ok; fi
# if [ -e /root/test1.txt ]; then echo ok; fi