Freaks City

Project Overview This project involves creating a minimal shell implementation in Linux that supports basic file and directory operations. The shell should provide an interactive command-line interface and execute common system commands. Core Functionality Requirements Display command prompt with current directory Process user input commands P ...

Logical Operators && - Logical AND || - Logical OR ! - Logical NOT Integer Comparisons Traditional numeric comparison operators: -eq - Equal -ne - Not equal -gt - Greater than -ge - Greater than or equal -lt - Less than -le - Less than or equal Alternative syntax using double parentheses: (("5" < "10")) ((&qu ...

Using Standard Redirection The most straightforward way to empty a file is by using the shell redirection operator > without a preceding command. This truncates the file to zero length immediately. > server.log Using the Colon or True Command The : (colon) is a shell built-in command that does nothing and returns a success status ...

# Print the last line of a file sed -n '$p' ok.txt # Output total number of lines sed -n '$=' ok.txt # Count blank lines sed -n '/^$/=' ok.txt Line Selection and Printing # Print odd-numbered lines (1st, 3rd, 5th, ...) seq 10 | sed -n '1~2p' # Print even-numbered lines (2nd, 4th, 6th, ...) seq 10 | sed -n '2~2p' Inserting Content sed '5 a ...

Vim Process inspection: ps -ef | grep PID Delete text: Ctrl+U: Remove all characters before cursor Ctrl+K: Remove all characters after cursor Batch replacement in Vim: :%s/old/new/g Example: :%s/docker\.io/registry.cn-hangzhou.aliyuncs.com\/acs-sample/g Paste formatted code: :set paste Show line numbers: :set nu Delete all content: :%d ...

When managing a small number of machines, handling them one by one might be acceptable. However, when dealing with dozens or hundreds of machines, repeating the same commands manually becomes tedious and error-prone. A more efficient approach is to write batch processing shell scripts. This article documents several batch processing scripts, in ...

Overview of expr The expr command is used for integer arithmetic and string operations (like length and pattern matching) in shell scripts. 1. Syntax and Basic Usage Only integer arithmetic is supported. Operators and numbers must be separated by spaces; otherwise, errors occur. The multiplication operator (*) must be escaped. When using expr i ...

In Linux shells, redirection alters the source or destination of data streams used by commands. Input redirection changes where a program reads its input from, while output redirection changes where it sends its results. By default, standard input comes from the keyboard (file descriptor 0), and standard output and error go to the terminal (des ...

Variable Deletion and Replacement Removing Prefix Patterns Removing the shortest matching prefix pattern using #: greeting="Hello World, Welcome to Shell" echo $greeting greeting_clean=${greeting#*or} echo $greeting_clean Removing the longest matching prefix pattern using ##: greeting_long=${greeting##*or} echo $greeting_long String ...

In Linux, removing a symbolic link that points to a directory with rm -rf can produce unexpected results depending on whether a trailing / is appended to the path. Careless use of the slash may delete contents of the original directory. Create a test directory and a symlink: $ mkdir -p ~/workspace/project $ echo "some content" > ~/ ...