Intro to Programming ROBERT SEDGEWICK | KEVIN WAYNE COMMAND-LINE INTERFACE ‣ brief overview ‣ live demo http://introcs.cs.princeton.edu Alan Kaplan and Kevin Wayne Last updated on 2/21/17 9:31 AM COMMAND-LINE INTERFACE ‣ brief overview ‣ live demo http://introcs.cs.princeton.edu Today’s plan: command-line interface Brief overview. ・IDE vs. command line. ・Files and file systems. Live demo. ・Navigating the file system. ・Java commands (including accessing stdlib.jar). ・Redirection and piping of standard input and output. Note: you will need CLI for the Assignment 2. 3 Integrated development environment (IDE) IDE. App designed for developing software. “compile” button “run” button pseudo-command line 4 Command-line interface Command line. App where you type commands. 5 Convergence: Linux, OS X, and Windows (September 1991) 6 Convergence: Linux, OS X, and Windows (March 2001) 7 Convergence: Linux, OS X, and Windows (August 2016) 8 Software for program development: tradeoffs Command line advantages. ・More control over system. ・Approach works with any language. ・Easy to automate tasks via scripting. IDE advantages. ・More intuitive for novices. ・Language-specific features. This course. Use IDE to edit and compile; use command line to execute. Beyond. Many other platforms embrace command line. 9 Files File. Sequence of bits stored on a computer. Filename. String that uniquely identifies a file. Mac OS X. /Users/wayne/cos126/hello/HelloWorld.java note: forward vs. backward slash Windows. C:\Users\wayne\cos126\hello\HelloWorld.java 10 File system hierarchy Directory (folder). Collection of files and other folders. root directory / Users Library Applications wayne DrJava.app Firefox.app Desktop cos126 Documents Music hello loops Hello.mp4 Für Elise.mp4 readme.txt RandomWalker.class RandomWalker.java /Users/wayne/cos126/loops/RandomWalker.java 11 COMMAND-LINE INTERFACE ‣ brief overview ‣ live demo http://introcs.cs.princeton.edu Live demo of file system commands 13 Standard input and output abstractions Command-line arguments. Provide arguments (strings) to a program. Standard output stream. Abstraction for writing output (default = screen). Standard input stream. Abstraction for reading input (default = keyboard). standardstandardstandard input inputinput command-linecommand-linecommand-line argumentsargumentsarguments standardstandardstandard output outputoutput standard audio standard drawing AA bird’s-eyebird’s-eye viewview ofof aa JavaJava programprogram (revisited)(revisited) A Abird’s-eye bird’s-eye view view of ofa Javaa Java program program (revisited) (revisited) 14 Live demo of standard input and output commands 15 Navigating the file system Action Mac OS X Terminal Windows Command Prompt print current directory pwd cd list contents of ls dir current directory move down cd introcs one subdirectory move up cd .. one subdirectory move down cd introcs/hello cd introcs\hello multiple subdirectories move to cd /Users/wayne cd \Users\wayne specified directory copy, move, remove, make cp mv rm copy move del directory, remove directory mkdir rmdir mkdir rmdir cycle through <Up Arrow> <Down Arrow> command history autocomplete javac Hello<Tab> 16 Java commands Action Mac OS X Terminal Windows Command Prompt compile Java program javac HelloWorld.java execute Java program java HelloWorld compile Java program javac-introcs HelloWorld.java (with our standard libraries) execute Java program java-introcs HelloWorld (with our standard libraries) file globbing javac *.java Java compiler version javac -version Java runtime version java -version 17 Command-line arguments, redirection, and piping Action Mac OS X Terminal Windows Command Prompt command-line arguments java Program arg1 arg2 redirect standard input java Program < input.txt redirect standard input java Program > output.txt piping java Program1 | java Program2 view contents, one more < input.txt screenful at a time java Program | more java Program1 < input.txt | more combinations java Program < input.txt > output.txt java Program1 arg1 | java Program2 arg2 terminate program <Ctrl-C> signal end-of-file <Ctrl-D> <Ctrl-Z> (when typing standard input) 18.