As shown below:
-b file is true if the file exists and is a block special file
-c file is true if the file exists and is a character special file
-d file True if the file exists and is a directory
-e file True if the file exists
-f file True if the file exists and is a rule file
- g file true if the file exists and the SGID bit is set
-h file true if the file exists and is a matching link
-k file true if the file exists and the "sticky" bit is set The value of
-p file is true if the file exists and is a named pipe
-r file is true if the file exists and is readable
-s file is true if the file exists and its size is greater than Zero, true
-u file True if the file exists and the SUID bit is set
-w file True if the file exists and is writable
-x file True if the file exists and is writable True if executed
-o file True if the file exists and is owned by a valid user ID
-z string True if the string length is 0
-n string If If the string length is not 0, then it is true
string1 = string2 If the two strings are equal, it is true
string1 != string2 If the two strings are not equal, it is true
int1 -eq int2 True if int1 is equal to int2
int1 -ne int2 True if int1 is not equal to int2
int1 -lt int2 True if int1 is less than int2
int1 -le int2 if int1 is less than or equal to int2, then it is true
int1 -gt int2 If int1 is greater than int2, it is true
int1 -ge int2 If int1 is greater than or equal to int2, it is true
!expr If expr is False then the compound expression is true. expr can be any valid test expression
expr1 -a expr2 If both expr1 and expr2 are true, then the integer is true
expr1 -o expr2 If either expr1 or expr2 is true, then the integer is true
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Python and C each have their own advantages, and the choice should be based on project requirements. 1) Python is suitable for rapid development and data processing due to its concise syntax and dynamic typing. 2)C is suitable for high performance and system programming due to its static typing and manual memory management.

Choosing Python or C depends on project requirements: 1) If you need rapid development, data processing and prototype design, choose Python; 2) If you need high performance, low latency and close hardware control, choose C.

By investing 2 hours of Python learning every day, you can effectively improve your programming skills. 1. Learn new knowledge: read documents or watch tutorials. 2. Practice: Write code and complete exercises. 3. Review: Consolidate the content you have learned. 4. Project practice: Apply what you have learned in actual projects. Such a structured learning plan can help you systematically master Python and achieve career goals.

Methods to learn Python efficiently within two hours include: 1. Review the basic knowledge and ensure that you are familiar with Python installation and basic syntax; 2. Understand the core concepts of Python, such as variables, lists, functions, etc.; 3. Master basic and advanced usage by using examples; 4. Learn common errors and debugging techniques; 5. Apply performance optimization and best practices, such as using list comprehensions and following the PEP8 style guide.

Python is suitable for beginners and data science, and C is suitable for system programming and game development. 1. Python is simple and easy to use, suitable for data science and web development. 2.C provides high performance and control, suitable for game development and system programming. The choice should be based on project needs and personal interests.

Python is more suitable for data science and rapid development, while C is more suitable for high performance and system programming. 1. Python syntax is concise and easy to learn, suitable for data processing and scientific computing. 2.C has complex syntax but excellent performance and is often used in game development and system programming.

It is feasible to invest two hours a day to learn Python. 1. Learn new knowledge: Learn new concepts in one hour, such as lists and dictionaries. 2. Practice and exercises: Use one hour to perform programming exercises, such as writing small programs. Through reasonable planning and perseverance, you can master the core concepts of Python in a short time.

Python is easier to learn and use, while C is more powerful but complex. 1. Python syntax is concise and suitable for beginners. Dynamic typing and automatic memory management make it easy to use, but may cause runtime errors. 2.C provides low-level control and advanced features, suitable for high-performance applications, but has a high learning threshold and requires manual memory and type safety management.


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