利用ChatGPT快速看懂别人的代码

ChatGPT可以加速我们学习的速度，比如下面这篇文章里的代码，看不懂的话，可以让ChatGPT帮你解释！！！

链接里这篇文章教大家如何在Linux系统中查看自己对某个文件的权限，但由于本人Linux基础薄弱，看不懂作者的代码，于是向ChatGPT求助。

You:

can you explain the following codes?

ChatGPT:

Of course! Please provide the codes you would like me to explain, and I’ll do my best to help you understand them.

You:

#！/bin/bash

#######################################  check_permission  ##########################################

function check_permission(){
 file_or_dir=$1

 ## 判断参数是否为空

 if [[ "$file_or_dir" = "--help" ]] || [[ "$file_or_dir" = "-h" ]]; then
 echo "Usage: "
 echo 'cdwin "Z:xxxcurrent" '
 echo 'check_permission ae.sas7bdat'
 return 1
 fi

 # 判断目录或文件是否存在

 if [ ! -e "$file_or_dir" ];then
 echo "filename or dirname does not exist."
 return 1
 fi

 # 判断是否有读权限

 if [ -r "$file_or_dir" ];then
 echo "$file_or_dir has read permission."
 else
 echo "$file_or_dir does not have read permission."
 fi

 # 判断是否有写权限

 if [ -w "$file_or_dir" ];then
 echo "$file_or_dir has write permission."
 else
 echo "$file_or_dir does not have write permission."
 fi

 # 判断是否有执行权限

 if [ -x "$file_or_dir" ]; then
 echo "$file_or_dir has execute permission."
 else
 echo "$file_or_dir does not have execute permission."
 fi
}&lt;/pre&gt;

# 4.Notes:

*   只支持单个文件或目录权限查询，如果需要批量查询可以使用循环（可优化）。如下：

### 查看全部权限列表

$ cdwin "Z:xxxcurrent"
$ ls | while read id; do check_permission $id; done;
aecm.sas7bdat has read permission.
aecm.sas7bdat has write permission.
aecm.sas7bdat has execute permission.
ae.sas7bdat has read permission.
ae.sas7bdat has write permission.
ae.sas7bdat has execute permission.

### 查看目录下没有可读权限的文件

$ cdwin "Z:xxxcurrent"
$ ls | while read id; do check_permission $id | grep "does not have read permission" ;done

ChatGPT:

The provided code is a bash script that defines a function called check_permission. This function is used to check the permissions of a file or directory. Let’s go through the code step by step:

The shebang #!/bin/bash indicates that the script should be executed using the Bash shell.
The function declaration function check_permission() defines the check_permission function.
The first few lines of the function handle the case where the user passes --help or -h as an argument. It displays usage instructions and returns with a status of 1 to indicate an error.
The script checks whether the file or directory exists by using the -e test condition. If the file or directory doesn’t exist, it displays an error message and returns with a status of 1.
The script then checks for read (-r), write (-w), and execute (-x) permissions using corresponding test conditions. It uses the provided variable $file_or_dir as the target for these checks.
If a permission is present, it prints a message indicating that the file or directory has the corresponding permission. Otherwise, it prints a message indicating that the permission is not present.
The script includes some comments to provide explanations and examples of usage.
The script suggests using a loop to check permissions for multiple files or directories. It provides an example using a loop with the ls command to list files and then calling the check_permission function on each file.

In summary, this script defines a function check_permission that takes a file or directory as an argument and checks for read, write, and execute permissions on it. It provides usage instructions and handles error cases.

感觉还是看不懂，那就再详细一点！！！

You:

can you explain more it in more detail? I don’t know much about shell scripts

ChatGPT:

Certainly! Let’s break down the code further and explain each part in more detail:

#!/bin/bash

This line is called a shebang. It specifies the interpreter to be used to execute the script, in this case, the Bash shell.

function check_permission(){
    file_or_dir=$1
    # ...
}

This block of code defines a function named check_permission. Functions allow you to group a set of commands together to perform a specific task. In this case, the function takes one parameter, file_or_dir, which represents the file or directory whose permissions we want to check.

if [[ "$file_or_dir" = "--help" ]] || [[ "$file_or_dir" = "-h" ]]; then
    echo "Usage: "
    echo 'cdwin "Z:xxxcurrent" '
    echo 'check_permission ae.sas7bdat'
    return 1
fi

This if statement checks if the value of file_or_dir is either --help or -h, indicating that the user wants to see the usage instructions. If so, it prints out some usage instructions and returns with a status of 1 using the return statement. A status of 1 typically indicates an error or failure.

if [ ! -e "$file_or_dir" ]; then
    echo "filename or dirname does not exist."
    return 1
fi

This if statement checks if the file or directory specified by file_or_dir does not exist (-e is a test condition for existence). If it doesn’t exist, it prints an error message and returns with a status of 1.

if [ -r "$file_or_dir" ]; then
    echo "$file_or_dir has read permission."
else
    echo "$file_or_dir does not have read permission."
fi

This if statement checks if the file or directory specified by file_or_dir has read permission (-r is a test condition for read permission). If it does have read permission, it prints a message indicating so. Otherwise, it prints a message indicating that it does not have read permission. Similar if statements are used to check for write and execute permissions.

The script includes additional comments that provide explanations and examples of usage. The provided examples demonstrate how to use the script to check permissions for multiple files or directories using a loop.

I hope this helps in understanding the script better. Let me know if you have any further questions!

再详细一点！！！

You:

more detail

ChatGPT:

Certainly! Let’s go into more detail for each part of the script:

#!/bin/bash

This line is called the shebang. It tells the operating system that this script should be run with the Bash shell.

function check_permission(){
    file_or_dir=$1
    # ...
}

This code defines a function named check_permission that takes one parameter, file_or_dir. The parameter is assigned to the variable $file_or_dir within the function.

if [[ "$file_or_dir" = "--help" ]] || [[ "$file_or_dir" = "-h" ]]; then
    echo "Usage: "
    echo 'cdwin "Z:xxxcurrent" '
    echo 'check_permission ae.sas7bdat'
    return 1
fi

This if statement checks if the value of $file_or_dir is either --help or -h. If it is, it means the user wants to see the usage instructions. The script then echoes (prints) usage instructions on the console using the echo command. The return 1 statement exits the function with a status of 1, indicating an error or failure.

if [ ! -e "$file_or_dir" ]; then
    echo "filename or dirname does not exist."
    return 1
fi

This if statement checks if the file or directory specified by $file_or_dir does not exist using the -e test condition. If it doesn’t exist, the script echoes an error message and returns with a status of 1.

if [ -r "$file_or_dir" ]; then
    echo "$file_or_dir has read permission."
else
    echo "$file_or_dir does not have read permission."
fi

This if statement checks if the file or directory specified by $file_or_dir has read permission using the -r test condition. If it has read permission, the script echoes a message indicating so. Otherwise, it echoes a message indicating that it does not have read permission. Similar if statements are used to check for write (-w) and execute (-x) permissions.

The script includes additional comments that provide explanations and examples of usage. These comments suggest using a loop to check permissions for multiple files or directories.

For example:

$ cdwin "Z:xxxcurrent"
$ ls | while read id; do check_permission $id; done;

This example uses the cdwin command (which might be defined elsewhere in your script) to change the directory to “Z:xxxcurrent”. Then it lists the files in that directory using ls and pipes (|) the output to a while loop. The loop reads each file name (stored in the variable id) and calls the check_permission function on each file.

I hope this provides a more detailed understanding of the script. Let me know if you have any further questions!

看不懂的地方，再次询问！！！

You:

I don’t know the ‘if’ statement in shell script

ChatGPT:

Certainly! In shell scripting, the if statement is used for conditional branching. It allows you to execute certain commands or blocks of code based on whether a condition is true or false.

The basic syntax of the if statement in shell script is as follows:

if condition; then
    # code to be executed if condition is true
else
    # code to be executed if condition is false
fi

Here’s a breakdown of each part:

The if keyword starts the conditional statement.
The condition is an expression or a command that returns an exit status (0 for success, non-zero for failure). The condition is typically enclosed in square brackets ([]) or double brackets ([[]]), and it can involve various comparison operators (-eq, -ne, -lt, -gt, etc.) or logical operators (&&, ||, !).
The then keyword indicates the code block to be executed if the condition evaluates to true (i.e., the exit status is 0).
The code block after then is indented and contains the commands or code that will be executed if the condition is true.
The else keyword is optional. It is followed by another indented code block that contains the commands or code to be executed if the condition is false.
The fi keyword marks the end of the if statement.

Here’s an example to illustrate the usage of the if statement:

#!/bin/bash

number=42

if [ $number -eq 42 ]; then
    echo "The number is 42."
else
    echo "The number is not 42."
fi

In this example, the condition [ $number -eq 42 ] compares the value of the variable $number with 42 using the -eq operator. If the condition is true, it executes the code block after then, which echoes “The number is 42.” Otherwise, if the condition is false, it executes the code block after else, which echoes “The number is not 42.” Finally, the fi keyword marks the end of the if statement.

That’s the basic usage of the if statement in shell scripting. You can build more complex conditions using logical operators (&&, ||) and combine multiple if statements to create nested conditions.

看不懂的地方，再次询问！！！

You:

“=” in condiction

ChatGPT:

In shell scripting, the = operator is used for string comparison within the condition of an if statement. It checks if two strings are equal. Here’s an example:

#!/bin/bash

name="John"

if [ "$name" = "John" ]; then
    echo "Hello, John!"
fi

In this example, the condition [ "$name" = "John" ] compares the value of the variable $name with the string “John”. The [ and ] brackets are used for command substitution and grouping. The double quotes around "$name" are used to handle cases where the string may contain spaces or special characters.

If the condition is true, it executes the code block after then, which in this case echoes “Hello, John!” to the console. If the condition is false, the script will continue executing the next section of code after the fi statement.

It’s important to note that within the condition, the = operator performs string comparison. If you need to perform numerical comparison, you would use -eq, -lt, -gt, etc., operators instead.

Additionally, you may come across the == operator in some shell scripts. While it works in many cases, it is not POSIX-compliant. To ensure maximum compatibility, it’s recommended to use = for string comparison within an if statement.

So, to summarize, the = operator is used for string comparison in the condition of an if statement. It checks if two strings are equal.

看不懂的地方，再次询问！！！

You:

means of “!” in ‘if’ condition , short answer

ChatGPT:

In the context of an if condition in shell scripting, the ! symbol is used as the logical NOT operator. It negates the result of a condition.

For example:

#!/bin/bash

name="John"

if [ ! "$name" = "Jane" ]; then
    echo "Hello, not Jane!"
fi

In this example, the condition [ ! "$name" = "Jane" ] checks if the value of the variable $name is not equal to the string “Jane”. The ! operator negates the result of the condition. If the condition is true (i.e., $name is not “Jane”), it executes the code block after then and echoes “Hello, not Jane!”.

So, in short, ! in an if condition is used as the logical NOT operator to negate the result of a condition.

看不懂的地方，再次询问！！！

You:

means of “-e” in ‘if’ condition , short answer

ChatGPT:

In the context of an if condition in shell scripting, the -e flag is used to check if a file or directory exists.

For example:

#!/bin/bash

file="/path/to/file.txt"

if [ -e "$file" ]; then
    echo "File exists."
fi

In this example, the condition [ -e "$file" ] checks if the file specified by the variable $file exists. If the file exists, it executes the code block after then and echoes “File exists.”

So, in short, -e in an if condition is used to check if a file or directory exists.

看不懂的地方，再次询问！！！

You:

means of “-r” in ‘if’ condition , short answer

ChatGPT:

In the context of an if condition in shell scripting, the -r flag is used to check if a file has read permission.

For example:

#!/bin/bash

file="/path/to/file.txt"

if [ -r "$file" ]; then
    echo "File has read permission."
fi

In this example, the condition [ -r "$file" ] checks if the file specified by the variable $file has read permission. If the file has read permission, it executes the code block after then and echoes “File has read permission.”

So, in short, -r in an if condition is used to check if a file has read permission.

看不懂的地方，再次询问！！！

You:

means of “-w” in ‘if’ condition , short answer

ChatGPT:

In the context of an if condition in shell scripting, the -w flag is used to check if a file has write permission.

For example:

#!/bin/bash

file="/path/to/file.txt"

if [ -w "$file" ]; then
    echo "File has write permission."
fi

In this example, the condition [ -w "$file" ] checks if the file specified by the variable $file has write permission. If the file has write permission, it executes the code block after then and echoes “File has write permission.”

So, in short, -w in an if condition is used to check if a file has write permission.