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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 ...

Navigating the Filesystem pwd Command pwd Displays the absolute path of the current working directory. cd Command cd [target_directory] Changes the current shell session's working directory. Usage: cd ..: Move up to the parent directory. cd /home/user/docs: Navigate using an absolute path (starts from root /). cd ../projects: Navigate using ...

pwd: Print Working Directory The pwd utility outputs the absolute path of the current working directory. It is primarily used to verify your location within the filesystem hierarchy before executing path-dependent operations. Syntax pwd [options] Usage Example $ cd /var/log/nginx $ pwd /var/log/nginx cd: Change Directory The cd command ...

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 ...