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This article mainly talks about "what are the shell programming methods of linux". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn "what are the shell programming methods of linux"?

1. For and while loop structure:

Before I write this, I'd like to remind you that this is the same as the for and whil loop structure we wrote in c and C++, but the rules are slightly different, that's all.

1. For loop structure format and practical demonstration:

A, for circular writing format:

For variable name in value list

Do

Command sequence

Done

B. Case demonstration:

#! / bin/bash

For i in 1 2 3 4 5

Do

Echo $I

Done

The result of the demonstration:

Root@txp-virtual-machine:/home/txp# source test.sh

one

two

three

four

five

2. While loop structure format and practical demonstration:

A, while circular writing format:

While conditional test operation

Do

Command sequence

Done

B. Case demonstration:

#! / bin/bash

I, 1

Jargon 10

While [$I-lt $j]

Do

Echo $I

ITunes $(($item1))

Done

The result of the demonstration:

Root@txp-virtual-machine:/home/txp# source test.sh

one

two

three

four

five

six

seven

eight

nine

Note: there are spaces on both sides of [] after while, semicolons after [] (if do is on one line), and there are two parentheses in the writing of iCom +.

2. Case statement:

Case statements in shell are born without break and do not require break, unlike switch case in the C language. By default, case in shell matches which execution, and does not say that it will execute other case after execution (just as the case language in shell comes with break by default).

1. The format of the case statement:

Case variable value in

Mode 1)

Command sequence 1

Mode 2)

Command sequence 2

.

*)

Default command sequence

Esac

2. Case demonstration:

#! / bin/bash

Var=9

Case $var in

8)

Echo "8"

9)

Echo "9"

Esac

The result of the demonstration:

Root@txp-virtual-machine:/home/txp# source test.sh

nine

3. Call the parameters of the shell program:

I wonder if you have thought of the standard writing of the int main function in our c language when you see this

Int main (int argc, char * argv [])

This was introduced in the previous c language series (the parsing of parameters argv and argc in the c language main function), so I won't cover it here. Yes, our shell receives parameters from users, which is similar to this idea. The rules for passing parameters in our shell are:

$0 corresponds to the name of the current Shell script

$# corresponds to a total of several parameters

$* corresponds to the parameter values of all locations

$? Corresponding to displaying the return value of the execution of the last command

$1, $2, $3. Then they correspond to the parameter values of the nth position respectively.

Let's write a case demonstration:

#! / bin/bash

Echo $0 $? * $# $1 $2 $3

The result of the demonstration:

Root@txp-virtual-machine:/home/txp# source test.sh aa bb cc

Bash 0 aa bb cc 3 aa bb cc

Here we pay a little more attention to the transmission of our c language:

C language:. / a.out aa bb cc argc = 4, argv [0] =. / a.out, argv [1] is the first valid parameter

Notice that argc equals 4, which counts argv [0], but our shell does not include $0 in the incoming parameter statistics.

At this point, I believe you have a deeper understanding of "what are the shell programming methods of linux?" you might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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