Shell learning record (II)

read:

    read Command to read a line from standard input , And assign the value of each field of the input line to shell Variable

#!/bin/sh
read name
read name1
echo "$name It is a test"
echo "$name1 It is a test1"

The above code is saved as test.sh,name Receive standard input variables , The result will be :

[[email protected] ~]# sh test.sh
OK                     # The standard input 
OK1
OK It is a test        # Output 
OK1 It is a test        # Output 

Show no line breaks ：

echo -e "OK! \c" # -e  Open escape  \c  Don't wrap 

Show results directed to file ：

echo "It is a test" > myfile

Output string as is , Do not escape or take variables ( single quote )

a=100
echo '$a'

Output ：

$a

Show command execution results :

echo `date`

Be careful ：  It's back quotes here  `, Not single quotes  '.

The result will show the current date

2020 year  9 month  2 Japan   Wednesday  21 when 07 branch 18 second  CST

printf The escape sequence of ：

Shell test command :

test Commands can generally be converted to brackets and expressions ：[ expression ]

#!/bin/bash
num1=100
num2=100
if [ $num1 -eq $num2 ]
then
        echo " Two numbers are equal "
else
        echo " The two numbers are not equal "
fi

if test $[num1] -eq $[num2]
then
        echo " Two numbers are equal "
else
        echo " The two numbers are not equal "
fi

Output ：

 Two numbers are equal 
 Two numbers are equal 

There is also a string operator below 、 File test operators are not listed one by one