Shell Learning Notes (i)

1, the first line must be #! /bin/bash

#! indicates that the script uses the following interpreter to interpret the execution

2. Echo Print output

For example echo "Hello World" > Aa.txt

　　

3. Receiving parameters

#!/bin/bash

Name=$1

Age=$2

Sex=$3

echo "Name: $name; age: $age; Sex: $sex"

Operating effect:

4, accept the user input parameters

#！ /bin/bash

Read-p "Please input your name:" Name

echo "My name is $name"

READ: Waiting for user input, similar to scanner inside Java

-P: Prompt information

5, Judge If/then/elif/else/fi

Elif equivalent to else if

If must end with FI, otherwise an error will be made

For example: Judging by the age of a person he is a teenager, middle age or old age (here is the assumption that 1~20 is a teenager 21~60 is aged 600 or older milk year)

#！ /bin/bash
Read-p "Please input your Age:" Age
If [$age-lt 0]; Then
echo "Age is incorrect"
Else
If [$age-lt 20]; Then
echo "Younger"
elif [$age-lt 60]; Then
echo "Adult"
elif [$age-lt 120]; Then
echo "Older"
Else
echo "Age is incorrect"
Fi
Fi

Schedule

1. String judgment

STR1 = str2 When two strings have the same content, length is true
Str1! = str2 True when string str1 and str2 are not equal
-N str1 True when the length of the string is greater than 0 (string non-null)
-Z str1 True when the string length is 0 (empty string)
STR1 is True when string str1 is not empty

2, the number of the judgment

Int1-eq int2 Two numbers equal to True
Int1-ne Int2 Two number is true
INT1-GT Int2 int1 greater than Int2 is true
Int1-ge Int2 int1 greater than or equal to Int2 true
Int1-lt Int2 int1 Less than Int2 is true
Int1-le Int2 int1 less than or equal to Int2 true

3, the judgment of the document

-r file user readable as True
-W file user can write as true
-X file user can execute as true
-F file is true for regular files
-d file files are directory-True
-C File file is true for character special files
-B file files are true for block special files
-S file files non-0 o'clock True
-T file is true when the specified device is terminal (default = 1)

If the-e file file exists test-e filename
-S file is present and is a socket file
Whether the-p file exists and is a FIFO (pipe) file

The-u file file exists and has the Suid property
The-G file is present and has the Sgid property
The-K file is present and has the Sticky bit property
-s Fie file exists and is not a blank file

4. Complex logic judgment

-A and
-O or
! Non -

Shell Learning Notes (i)