What is CLI? • Run from the Terminal, e.g. a shell • They don’t need no stinkin' mouse • They can work with things like Expect • I can use them remotely without a GUI/ Web Browser • Computers can run them too!
Command Line Interfaces • Curses / NCurses • GNU ReadLine • STDIN, STDOUT, STDOUT • May require user interaction beyond the options, i.e. menus, prompts.
Enable Composability • I need to pipe your output to sort • I need to pipe input to your program • I need columnar data or the ability to affect the output record separator • At the very least, give me a plugin interface
Documentation • You need to write those docs before you show me your cool utility • Support --help if not --manual • Tell users where to go for more information • Maybe write a trendy blog post and throw it at reddit or HN
Example Uses • OMG, Major Pet Peeve • Show me how you use the tool • Show me how you expect arguments • Show me what you get when you run it! ... --start When to start --stop When to stop ...
CLI Tools in Perl • Prolific and Infinite • Specific to Generic • If you can, upload to CPAN!! • App::* • Great chance to see how others will use your code! • We are the glue of the internet, after all
Magic Diamond • Use the magic diamond to accept input • Consistent with expectations of UNIX tools • Can accept input from STDIN • Given a list of files, it reads their content while(my $line = <>) { chomp($line); next unless $line; ... }
use Getopt::Long::Descriptive ...and running "my-program --help" will produce: my-program [-psv] [long options...] -s --server server to connect to -p --port port to connect to -v --verbose print extra stuff --help print usage message and exit
use Term::ANSIColor • perldoc Term::ANSIColor • Colors can provide vital clues in large text dumps • Some users don't like them • Most people interact with git, check their ~/.gitconfig to see if they like colors?
Introducing CLI::Helpers • Wraps input and out operations for CLI utilities in neat ways • Based on years of writing personal and shared CLI tools • I like it, you might too!
CLI::Helpers Input use CLI::Helpers qw(:input); die "Aborting run" unless confirm("Are you sure?"); Inspired by IO::Prompt(er) but not in a confusing state of deprecation or maintenance or compatibility.
CLI::Helpers @ARGV From CLI::Helpers: --color Boolean, enable/disable color, default use git settings --data-file Path to a file to write lines tagged with 'data => 1' --debug Show developer output --debug-class Show debug messages originating from a specific package, default: main --quiet Show no output (for cron) --syslog Generate messages to syslog as well --syslog-debug Enable debug messages to syslog if in use, default false --syslog-facility Default "local0" --syslog-tag The program name, default is the script name --verbose Incremental, increase verbosity (Alias is -v)
CLI::Helpers Output output({clear=>1,sticky=>1}, "Thanks for using my great utility!" ); output( "Hello, World!", " This is going to be awesome.", " Please enjoy." );
CLI::Helpers Output $ perl clih.pl Thanks for using my great utility! Hello, World! This is going to be awesome. Please enjoy. Thanks for using my great utility!
CLI::Helpers Debug output("Hello, World!"); debug({clear=>1}, sprintf "EYES ONLY: it is %d!", time ); verbose({indent=>1}, "And hello to you, fine sir.");
CLI::Helpers Debug $ perl clih.pl Hello, World! $ perl clih.pl --verbose Hello, World! And hello to you, fine sir. $ perl clih.pl --debug Hello, World! EYES ONLY: it is 1466366341! And hello to you, fine sir.
CLI::Helpers Data Files $ perl clih.pl --data-file test.out Hello, World! one two three four five $ cat test.out one two three four five output("Hello, World!"); my @row = qw(one two three four five); output({data=>1}, join("\t", @row));
CLI::Helpers Output Options color Term::ANSIColor color word clear Number of new lines before text sticky Text output in line and then again at termination indent Indentation level level Number of v's syslog_level Syslog severity level no_syslog Even if --syslog is present, don't syslog this line IMPORTANT Even if --quiet is enabled, output this line stderr Output this line to STDERR instead of STDOUT data This line will go to the data file
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