Bash Shell Scripting Basics

Positional Parameters

• Positional parameters are used to access arguments passed to a shell script
• The first nine arguments can be accessed using $1, $2, ..., $9
• Arguments beyond the ninth can be accessed using ${10}, ${11}, and so on

Special Parameters

• Special parameters are predefined variables that hold special meanings and values in a script
• $0: holds the name of the script or shell itself
• $1, $2, $3...: represent the command-line arguments passed to the script
• $#: represents the number of command-line arguments passed to the script
• $*: represents all the command-line arguments passed to the script as a single string
• $@: represents all the command-line arguments passed to the script as separate strings
• $?: holds the exit code of the last command executed in the script

Command Line Arguments

• Command line arguments refer to the values passed to a shell script or program when it is executed in the command line
• Command line arguments are stored in special variables called positional parameters
• The first argument is stored in $1, the second argument in $2, and so on
• $0 stores the name of the script or program itself

Control Flow and Conditional Statements

• The if statement is used to check conditions and execute commands based on the outcome
• The -n option is used to check if a string is not null
• The == operator is used to check for string equality

Exit and Exit Status of a Command

• Every command that is executed returns an exit status
• The exit status is an integer value that indicates whether the command has executed successfully or encountered an error
• The exit status can be checked using the $? variable in the shell
• The exit status ranges from 0 to 255, with 0 indicating successful execution and any non-zero value indicating an error
• The exit command is used to terminate the execution of a shell script or a command

Variable Commands

• read command: used to read input from the user and store it in a variable
• export command: used to export a variable to the environment
• typeset command: used to define or change the properties of a variable
• unset command: used to delete a variable

Learn about accessing arguments in bash shell scripts. Understand how to use positional parameters and their syntax in shell scripting. Test your knowledge with this quiz!