tailieunhanh - Module Linux essentials - Module 4: Command line skills

This module provide basics of using the Linux command line. After studying this chapter you should be able to: Understanding the basic shell; working with formatting commands and options, learn the effects of variables, globbing and quoting. | Module 4 Command Line Skills Exam Objective Basics of using the Linux command line Objective Summary Understanding the basic shell Working with formatting commands and options Learn the effects of variables, globbing and quoting CLI or Basic Shell The Command Line Interface Text based interface Access via a Terminal GUI-based terminals Virtual terminals Commands passed to a shell Shell prompt: [sysadmin@localhost ~] Shell Features Command history – ability to re-execute previous commands quickly Scripting – create programs by placing shell commands in a file to run Alias – create shortcuts to longer commands Variables – store information that can be used to modify the functionality of the shell or commands Understanding Command Structure Command format Basic format: command [options] [arguments] Options change the behavior of command Arguments are used to provide additional information for a command Command options Vary based on command Older option format: -a Can be combined: -abc = -a -b -c Newer (GNU) option format: --all Command History View previous commands: history Bring up previous commands: up arrow Modify previous commands: left arrow, right arrow, etc. Execute a previous command: ! Variables Shell Variables Used to store system information View with echo command: echo $HISTSIZE Modify: HISTSIZE = 500 Changes are temporary Place commands in ~/.bashrc to make permanent PATH Variable Determines where commands are executed from May need to be modified for custom software Example: Command Path and Aliases Find command location Hard to determine where a command is located Instead of searching directories in the PATH variable manually, use the which command: which cal which date Aliases Used to make shortcuts for longer commands View aliases: alias Create alias: alias name=command Change are temporary To make permanent, place alias command in ~/.bashrc file Additional Command Structure Globbing Used to match sets of files in a directory * = match zero or more of any characters ? = match exactly one of any character [ ] = match exactly one of a set of characters: echo [abc]*.txt echo [!abc]*.txt Quoting Double quotes – used to disable the meaning of some metacharacters, like glob characters Single quotes – used to disable the meaning of all metacharacters Can use \ to disable next character only Backquotes – used to execute a command within another command line Control Statements The ; character - Used to separate commands on a command line The && characters – Used to execute the second command if the first command succeeds The || characters – Used to execute the second command if the first command fails | Module 4 Command Line Skills Exam Objective Basics of using the Linux command line Objective Summary Understanding the basic shell Working with formatting commands and options Learn the effects of variables, globbing and quoting CLI or Basic Shell The Command Line Interface Text based interface Access via a Terminal GUI-based terminals Virtual terminals Commands passed to a shell Shell prompt: [sysadmin@localhost ~] Shell Features Command history – ability to re-execute previous commands quickly Scripting – create programs by placing shell commands in a file to run Alias – create shortcuts to longer commands Variables – store information that can be used to modify the functionality of the shell or commands Understanding Command Structure Command format Basic format: command [options] [arguments] Options change the behavior of command Arguments are used to provide additional information for a command Command options Vary based on command Older option format: -a Can be combined: .