Shulou(Shulou.com)06/01 Report--

1. The basic format and variables of shell

# add an interpreter to the shell script #! / bin/bash

# print out hello world with script

#! / bin/bash

Echo "hello world"

Exit

Parameter: a parameter is an entity that stores real values, which is generally referenced in the script

# using variables to echo hello world, the following example echoes two hello world.

#! / bin/bash

A = "hello world"

Echo $a

Echo "hello world"

Exit

If something else is added after the parameter, you need to use {}

#! / bin/bash

A = "hello world"

Echo ${a}, i am coming

Exit

Echo result:

# calculate string length, hello world with spaces, a total of 11

2. Script exit

# the return value of a script that executes successfully is 0. If it is not successful, it is not 0.

[root@localhost script] # clear

[root@localhost script] # sh hello.sh

Hello world,i am coming

eleven

[root@localhost script] # echo $?

0

# determine whether there is a file in a directory. If so, echo file exsit. If not, return 1.

[root@localhost script] # cat test.sh

#! / bin/bash

Cd / home

If [- f file]; then

Echo "file exsit"

Else

Exit 2

Fi

[root@localhost script] # sh test.sh

[root@localhost script] # echo $?

two

[root@localhost script] #

3. Test statement, if statement

Whether the test-d xx directory exists

Whether the test-f xx file exists

Whether test-b xx is a block file

Is test-x xx an executable file

A-eq B judges whether they are equal or not.

A-ne B judgment is not equal

A-le B is less than or equal to

A-lt B less than

A-gt B is greater than

# if conditional judgment statement

If []; then

.

Else

.

Fi

# if statement nesting

If []; then

.

Elif []; then

.

Elif []; then

.

Else

.

Fi

# test gives an example to determine whether the test file exists, and if so, back up it. If the message is not echoed

# example: enter a value to determine which interval it is in. Less than 80, greater than 100, between 80 and 100, using if nesting!

[root@localhost script] # cat if.sh

#! / bin/bash

Read-p "plz input a $num:" num

If [$num-le 80]; then

Echo "num is less 80"

Elif [$num-ge 80] & & [$num-le 100]; then

Echo "num between 80 and 100"

Else

Echo "num is greater than 100"

Fi

4. Circular statements for, while

For var in $var1 $var2 $var3 var4... $var

Do

.

.

Done

# example: print 1 to 10 numbers

[root@localhost home] # cat for1.sh

#! / bin/bash

For var in {1..10}

Do

Echo "$var"

Sleep 2

Done

[root@localhost home] # sh for1.sh

one

two

three

four

five

six

seven

eight

nine

ten

[root@localhost home] #

# print box content for nesting

[root@localhost home] # sh for2.sh

*********

*********

*********

*********

*********

*********

*********

*********

*********

[root@localhost home] # cat for2.sh

#! / bin/bash

For ((iTun1)

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