Does the shell in linux have system functions?

The shell in Linux has system functions; shell programming has system functions like other programming languages, and you can also customize functions. For example, you can use the basename system function to get the file name. The syntax is "basename [pathname] [suffix]", using the dirname system function to return the path part of the file, the syntax is "dirname file location".

#The operating environment of this tutorial: linux7.3 system, Dell G3 computer.

Does the shell in Linux have system functions?

The shell in Linux has system functions

Function introduction

Shell programming is the same as other programming languages. System functions can also be customized functions. Among the system functions, we will introduce two here.

1. System function

basename basic syntax

Function: Return the last / part of the complete path, often used to obtain File name

basename [pathname] [suffix]

basename [string] [suffix] (Function description: The basename command will delete all prefixes including the last ('/') character, and then display the string.

Option:

suffix is ​​the suffix. If suffix is ​​specified, basename will remove the suffix from pathname or string.

Application Example

Case 1: Please return/ The "aaa.txt" part of root/test-linux/aaa/aaa.txt

basename /root/test-linux/aaa/aaa.txt

You can use basename to get the file name. If you put the suffix, only the file name will be returned, without the suffix

dirname Basic syntax

Function: Return the part before the last / of the complete path, often used to return the path part

dirname Absolute file path (Function description: Remove the file name (non-directory part) from the given file name containing the absolute path, and then return the remaining path (directory part))

Application Example

Case 1: Please return /root/test-linux/aaa/aaa.txt of /root/test-linux/aaa

dirname /root/test-linux/aaa/aaa.txt

2. Custom function

Basic syntax

[ function ] funname[()]
{
Action;
[return int;]
}

Write the function name directly when calling: funname [value]

Application example

Case 1: Calculate the sum of two input parameters (dynamic acquisition), getSum

#!/bin/bash
#定义一个函数 getSum
function getSum(){
        SUM=$[$n1+$n2]
        echo "和是=$SUM"
}
#输入两个值
read -p "请输入一个数n1=" n1
read -p "请输入一个数n2=" n2
#调用自定义函数
getSum $n1 $n2

Recommended learning:

Linux video tutorial

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