What Is Perl Commonly Used For

It tries to match as many of the same characters as possible. Perl - What is the difference between die and exit in perl?. pm extn and is considered a separate namespace. The perl time function is used for the determination for how many seconds have passed since a certain date (most commonly Jan 1st 1970) you can find various methods online to determine this as. Go is an open source programming language that makes it easy to build simple, reliable, and efficient software. JavaScript, PHP and Perl are three of the most commonly-used programming languages on the Internet. For example, you might want to offer the results of a complicated computation as a server process to other processes on the network, perhaps directly accepting input from other processes on the network. Perl is an interpreted, free, open source programming language first developed by Larry Wall in 1987. already in existence to make writing new scripts easier. For example see the Perl Script dpx_timecode. grep searches for matches to pattern (its first argument) within the character vector x (second argument). It manages both authentication and authorization and provides headers for accounting. It is preferred over other programming languages as it is faster, powerful and Perl has a lot. (Since Perl 5. CGI programs (or scripts) are. This page describes the syntax of regular expressions in Perl. On the other hand, if you want to run multiple instances of some task from your Perl script, the other monks gave you good ideas - basically your options are processes or threads. On May 16, 2018, the Perl Foundation announced that search. Sharepoint throws: A supported MIME type could not be found that matches the content type of the response. Understand how to read and import spreadsheet files using basic R and packages. That "main::" part and. Regular Expression (Regex or Regexp or RE) in Perl is a special text string for describing a search pattern within a given text. Array names, as a whole, are prefixed with the @ sign followed by a letter or _ and can consist of either letters, numbers, or _ characters. Perl is used extensively in health informatics. org would be shut down on June 29, 2018 (after 19 years of operation), due to its aging codebase and maintenance burden. Regular expression denial of service vulnerability of WEBrick’s Digest authentication module was found. Although most database systems use SQL, most of them also have their own additional proprietary extensions that are usually only used on their system. Perl 5 had arrays, indicated by @ and indexed by integer, and hashes, preceded by % and keyed by string; on these blocks, the church of Perl was built. 10 years ago, Perl was more popular than it. • Perl runs on all platforms and is far more portable than C. What is Perl/CGI? Perl is a simple programming language. • Initially designed to monitor software projects and generate reports, Perl gained popularity. Sure, depending on what you want to show. But there is a difference. Instead of writing the code each time these commonly-performed tasks are needed, routines are created and called when these tasks need to be performed. In shells, redirection is used for file I/O. Older versions of R used the GNU library to implement both POSIX BRE and ERE. Sometimes these are termed as “Perl 5 Compatible Regular Expressions”. Now there's a problem; computers cannot understand high-level languages, which we humans can easily understand. What Is CGI. Due to their simplicity, they are very quickly accessed or queried, which makes them very useful for simple tasks. http, https and ajp - comparison and choice In a web scenario, client to server traffic is usually carried using an http (HyperText Transfer Protocol) transport. Recall two things from the discussion of CGI. Any directive that you can include in a. You'll learn to do something similar — but slightly more advanced — to show just how easy it is to get up and running with Perl. If this wasn't difficult enough, medicine also uses a large number of medical abbreviations. If Perl made a system call for every read operation, that would be 10,001 system calls in all (one extra to detect end-of-file), and if the file was on the disk, it would have to wait for the disk at least 10,000 times. com and Salon. Perl is a dynamic programming language, created in 1987 by Larry Wall, a linguist at NASA. The I-beam is the most common type used today. But by the time I was building my first websites for commercial use, PHP had taken over. Vape Shop Near Me. It was developed as a scripting language, meant to combine the best features of C, sed, and the Bourne Shell. Similar to $* in the Unix/Linux shell. A programming language is a systematic method to describe computations. The most common Perl platforms (Unix and Unix-like, Microsoft platforms, and VMS) have large enough testing and expert population that they are doing well. • Perl runs on all platforms and is far more portable than C. Since the interpreter actually does convert the program into byte code before executing it, it is sometimes called an interpreter/compiler. 1, new semantics in Perl 5. Beginners Introduction to Perl by Doug Sheppard 1. Perl - What is the difference between die and exit in perl?. A resource is some chunk of information that can be identified by a URL (it's the R in URL). Structure of a CGI Script. It doesn't have to be used on the web, it can run locally on your computer, but it's popular for use on the web. Back in 2007 when I first heard about Ruby, the alternatives were Perl, Java, and PHP. In the Replace box: Use $ (dollar) instead of \ (backslash) to replace references. There is just one little thing about Perl I don't like. The value returned is the value of the last expression evaluated, just as with subroutines. Perl supports some special characters in the pattern and can play some special roles. Dumpster diving ____ can be used to read PINs entered at ATMs or to detect long-distance authorization codes that callers dial. Without this support Perl 6 might as well not even exist for this group who already have to code for Perl versions a decade out of date in many cases. This has nothing to do with perl, except that "foo" is a common variable name used in perl. Schemes currently defined are as follows, with links to more details. As a multi-paradigm, dynamically typed language, Perl allows a great degree of flexibility in program design. In perl, comments are words within the program that perl itself. Nobody is trying to say Perl is as fast or faster than C, just that relatively, it's fast for the development cost it requires. htaccess file is better set in a Directory block, as it will have the same effect with better performance. I would appreciate if you provide me with examples. In the case of non-ISO-8859-1 characters (characters above FF hex/255 decimal in the Unicode set), they just can not be used in URLs, because there is no safe way to specify character set information in the URL content yet [RFC2396. Renaming a module is always a pain as you need to change the name of the file. Q45) How to use modules while working with this language? A module usually refers to a namespace which is mentioned in a file. Nobody really likes going into where things have been glued and pulling apart that glue and replacing it with something else, so people love to throw out the old glue and replace it with anything besides glue. steel w type i-beams: steel s type i-beams: steel channels: steel angles: aluminum channels: aluminum i-beams. Perl stands for Practical Extraction and Reporting Language. When it is formed into particular shapes and sizes, it is referred to as structural steel. No big whoop, “perl foreach” continues to be one of the most popular on Google searches for the language. Perl is especially good at parsing text, so. Common Practices Common Goofs for Novices Efficiency Programming with Style Fluent Perl Program Generation Chapter 25. so usage of =~ is very confusing. Perl is commonly known as an interpreted language, is not strictly true. sv_utf8_(downgrade|decode) are no longer marked as. Before Perl 5. Packages are perl files with. Perl used to be the most popular web programming language due to its text manipulation capabilities and rapid development cycle. Not only are back slashes needed for every line, some lines need two, then the old original AWK is used. Perl regular expressions by themselves are very powerful, but when used in tandem with UltraEdit's powerful Find/Replace engine, you can take your searches to a new level. The most common medical treatments for OCD are certain Serotonin Reuptake Inhibitors that can also be used to treat depression, including fluoxetine (Prozac) Abbey Perl. Created by Graham Barr and now a SourceForge project under development in conjunction with several individuals, perl-ldap offers a great collection of object-oriented modules used to communicate with an LDAP server. Perl is the most common language used for writing CGI scripts, and for very good reason. For example, you might want to offer the results of a complicated computation as a server process to other processes on the network, perhaps directly accepting input from other processes on the network. Though Perl is primarily used in Linux kind like environments with the web servers, it’s also gaining quite a lot of popularity among Mac OS systems and Windows-based system. Bio-Informatics Databases E-mail Handling with Perl Games and Multimedia GUI (Graphical User Interface) Development Multi-tasking and Networking Quality Assurance (QA) and Testing. It is a high-level programming language written by Larry Wall, specially designed for processing text. Eliot, taught for many years at Columbia University and at the University of Texas, and is now professor of English literature at Bar-Ilan University. This page is a basic tutorial on Windows's Environment Variables. If you are upgrading from an earlier release such as 5. We used the \Q. Watch Queue Queue. pdf to resume. Farina is made from soft wheat kernels and is the main ingredient of the hot cereals Cream of Wheat and Malt-O-Meal. pm in @INC at. JavaScript, PHP and Perl are three of the most commonly-used programming languages on the Internet. Logstash is an open source, server-side data processing pipeline that enables you to ingest data from multiple sources simultaneously and enrich and transform it before it is indexed into Elasticsearch. Strict and Warning are probably the two most commonly used Perl pragmas, and are frequently used to catch "unsafe code. Hire the best Perl Developers. The value may contain entities (e. POE is the first Perl module to support any event loop. Correct spelling for the English word "perl" is [ p_ˈɜː_l], [ pˈɜːl], [ pˈɜːl] (IPA phonetic alphabet). It gives you the power to embed Perl code in your HTML documents and the ability to build your Web site out of small reusable objects in an object-oriented style. This page lists the filename extensions, or suffixes, used in the source code. And the rise of Python. com Form Character Limit. I‘m a new Linux user. This means that all these radicals are essential. • Perl is very efficient in TEXT and STRING manipulation i. In English, sentences end with a period. Getting even a limited subset of the functionality to work in a shell script is often a useful first stage in project development. Piping Index of symbols. If Faker is used while writing in the Perl. The code here is tested on Windows 10. However, for users who just want to test something for an urgent requirement, it is pretty boring to put the test data in a file and access it using the open and readline functions. Effectively equivalen. Chapter 22 Using HTML FORMs with Perl CGI Scripts. Perl -l Option: Line separator handling. New in Perl 5 are ties—a way of intercepting accesses to a Perl variable (array, hash, scalar, or filehandle). You can do some really stupid things with Perl if you put your mind to it. PERL programming and application development in omics settings using these programming languages/tools. I fetch data from Sharepoint using perl on a linuxmachine. He is the founder and editor of Common Knowledge. All new computers come equipped with parallel multi-core processors. grep searches for matches to pattern (its first argument) within the character vector x (second argument). • Perl is very efficient in TEXT and STRING manipulation i. The value is expressed in hexadecimal , and may include a leading 0x. For example, to print only the second and sixth fields of the date command (the month and year) with a space separating them, at the Unix prompt, you would enter:. It is used to rename and move files and directories. net gateway transact dll URL. CGI is not a language. Thanks for the info. What can the Faker from Perl be used for? The Faker from Perl can be used to generate fake data. This is not the case on Solaris so I'm working on setup instructions that use the CPAN module to fetch dependent modules (eg perl -MCPAN -e 'install Cache::Cache'). pm in @INC at. Two implement POSIX ERE, while the third is based on PCRE. It would belong to the Perl Family of Languages, which includes such languages as Perl 4, Perl 5, Perl 6, Ruby, and even PHP. It is used for mission critical projects in the public and private sectors and is widely used to program web applications of all needs. CGI (Common Gateway Interface) Using Perl Sunnie Chung What is CGI ? • The Common Gateway Interface, or CGI, is a set of standards that define how information is exchanged between the web server and a custom script. It can do many, many other things, sometimes optimally compared to other programming languages, but handling text is definitely it's strength. on linux platforms you can try (as root): then as your user: warning, this command can return a lot of lines, so you'd better pipe the output to 'more'. Perl is a great language for people who know it already (like me), but Python seems to be (from my outsider's perspective) a better language for doing the sort of quick and dirty file and text parsing stuff that Perl used to be the "go-to" language for. For creating tools, primarily ones that digest and otherwise handle text from files. Below is a basic example of a Perl subroutine. Perl SAX (Simple API for XML) is a common parser interface for XML parsers. If we keep a secret, no one else knows about it. Book overview. The value is expressed in hexadecimal , and may include a leading 0x. Perl is an old language, been used for much more than a decade now. You want to determine whether a user entered a North American phone number in a common format, …. What is SAML? How it works and how it enables single sign on The Security Assertion Markup Language (SAML) standard defines how providers can offer both authentication and authorization services. The internet couldn't possibly run without someone somewhere writing some code, but in internet history, there are a few particular languages that provided the foundation upon which the web we know today is built. # -*- Mode: cperl; coding: utf-8; cperl-indent-level: 4 -*- package CPAN; $VERSION = '1. A Perl identifier is a name used to identify a variable, function, class, module, or other object. RTF is a document language used for exchanging text between different word processors and text-processing applications. If you are upgrading from an earlier release such as 5. perl (small 'p') is the program used to interpret the Perl language. This just completely fit in with what was going to be needed for the web, and Perl, as a scripting language that was easy to use, that more closely resembled natural language. CSV, Divider, Programming terms, Separator, Spreadsheet terms. A simple script can be used with ImageMagick to automatically increment the time code for each frame in a sequence. Read more about POE. Learn software, creative, and business skills to achieve your personal and professional goals. The command line arguments are in @ARGV. What is object-oriented Perl? Object-oriented Perl is a small amount of additional syntax and semantics, added to the existing imperative features of the Perl programming language. Perl is a family of languages, it regroups Perl5 and Perl6, Perl 6 is a fork of Perl5. pm included in Perl 5. We invoke the Read method from the interface. Is this version of Perl in the "rightbracket"? $;. Many of the bug fixes in 5. What if PTSD Is More Physical Than Psychological? was first used in artillery shells by the German Army in 1902. Perl: Strict, Warnings, and Taint. The final line of the module that writes the email letter calls on that subroutine. Sometimes it is termed as "Perl 5 Compatible Regular Expressions". The current version of CGI. What is Perl 3. This video is unavailable. Which is not the commonly used programming language for AI? a) PROLOG b) Java c) LISP d) Perl e) Java script. The most commonly used method is the Ziehl-Neelsen method, though there is also a Kinyoun's method. Shell metacharacters include things like pipes, redirects and statement separators: (ps -aux | column 1 > pids); date. Perl is a programming language which uses natural language elements, words that are used in common English language and is, therefore, easier to understand by humans [high-level language]. Instead of the Positional role used to implement arrays, the Associative role should be used to implement hashes. The most common Perl platforms (Unix and Unix-like, Microsoft platforms, and VMS) have large enough testing and expert population that they are doing well. If any of the file tests (or either the stat or lstat operator) is given the special filehandle consisting of a solitary underline, then the stat structure of the previous file test (or stat operator) is used, saving a system call. They are used to implement the command-line interfaces (which ship with the library). So what is Visual Basic used for ? I'm curious about the strengths of VB is comparison to other programming languages out there. Naming sub-schemes Different schemes usually use different protocols on the network. If EMTs want to communicate more effectively they must understand medical abbreviations. Perl is a procedural language with a bit of object oriented programming. pm in @INC at. already in existence to make writing new scripts easier. All that without using the word 'refactoring' even once. What Is Government Health Insurance What Is Government Health Insurance Do you know that, when you postpone some medical evaluation or perhaps assessment, you more often than not conclude paying out extra on medical expenditures, at a later time, when compared to if the original check as well as exam acquired been performed?. This is an area the needs more work (see Criteria section). The most common types of semolina are farina and durum semolina. So a package is nothing but group of related scalars,arrays,hashes and subroutines for a specific purpose. Tips No matter the shape or size of your penis you should learn to work around the best ways to enjoy sex with your partner. Commonly used of course but as you can see from the names - you can't tell what they are for. The term ‘PHP’ is used to define PHP Hypertext Processor language that is a free server-side scripting language that has been designed for not just web development but also as a general-purpose programming platform. The Perl scripting language is the designer's best friend in meeting milestone targets. Wild cards are 'dots' placed within the regex along with the required word to be searched. Writer Pearl S Buck; singer Pearl Bailey. Review the architecture of Perl DBI (The Perl Database Interface Module), what DBI provides to interact with databases, then cover simple tasks such as connecting and disconnecting from databases. They are most commonly used in metal buildings, though they sometimes replace closely spaced rafters in wood frame structures. Perl is considered for text processing which helps in reporting while Python is now a general-purpose language and currently being used in many fields. 0) Used to override the randomization of Perl's internal hash function. Help is available from other Windows Perl developers on the #win32 irc channel on irc. A CGI program can be written in any programming language, but Perl is one of the most popular. I hope it's true. It is also used for graphics programming, system administration, network programming, applications that require database access and CGI programming on the Web. Cron Job Basics Learn how the Cron Job tool can help you automate the scripts on your web site. Another common issue with regular expressions lies in the common expressions we use all the time; it seems like we're forever re-inventing the wheel!. RTF is a document language used for exchanging text between different word processors and text-processing applications. This program is free software; you can redistribute it and/or modify it under the terms of the Artistic License, which comes with Perl. This article describes how to provide reusable code using ties. You'll learn to do something similar — but slightly more advanced — to show just how easy it is to get up and running with Perl. This is not the case on Solaris so I'm working on setup instructions that use the CPAN module to fetch dependent modules (eg perl -MCPAN -e 'install Cache::Cache'). Perl is a scripting language widely used for system administration and programming on the World Wide Web. Written in Perl and offering the modern features you’ve come to expect in blog platforms, the site is hosted by Dave Cross and Aaron Crane, with a design donated by Six Apart, Ltd. Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Oh really? So that's why you came here. That "main::" part and. They are used by websites to carry out more complicated operations. Regular expression matching can be simple and fast, using finite automata-based techniques that have been known for decades. This time, we give an argument to the script to tell it the name of the directory, corresponding to the directory name in the openssl. So what attracted me to the language was actually the fact that I could understand what a piece of code was about without knowing much about programming. Perl regular expressions by themselves are very powerful, but when used in tandem with UltraEdit's powerful Find/Replace engine, you can take your searches to a new level. Two weeks ago, I wrote about the SEO workshop I’m running on Tuesday morning just before The Perl Conference in Glasgow this August. Perl Interview Questions 1) What is Perl? Perl stands for Practical Extraction and Reporting Language. Why CGI and not (PHP|ASP|Java Servlets)? Because CGI is still the most commonly used architecture for dynamic web pages - despite what you might hear from the marketing departments at Sun or Microsoft. Perl is a computer language. It facilitates the exchange of informaTon over the Web. Today, I’d like to give a few more details about the other workshop I’m running that day. Probably the only "legitimate" case, is if you made a typo, and that's how you ended up with a variable that is used only once. Unlike Perl, which is a general purpose scripting language that you can use for a wide variety of purposes (and not just generating web pages), PHP was designed from the ground up to be used for scripting web pages. Practical Extraction and Reporting Language, or Perl, is a multi-purpose programming language. Schemes currently defined are as follows, with links to more details. x series of GTK+ libraries. I am thinking it is a programming language because it contains. Perl is a scripting language which uses a syntax simliar to C/C++. A regular expression, often called a pattern, is an expression used to specify a set of strings required for a particular purpose. You'll learn to do something similar — but slightly more advanced — to show just how easy it is to get up and running with Perl. Which is not the commonly used programming language for AI? a) PROLOG b) Java c) LISP d) Perl e) Java script. Perl is one of the more commonly used languages in writing CGI scripts and programming for Internet and web page applications. Some common relational database management systems that use SQL are: Oracle, Sybase, Microsoft SQL Server, Access, Ingres, etc. Back in 2007 when I first heard about Ruby, the alternatives were Perl, Java, and PHP. PERL programming and application development in omics settings using these programming languages/tools. Yes, sometimes Perl looks like line noise to the uninitiated, but to the seasoned Perl programmer, it looks like the notes of a grand symphony. I think Perl tends to attract the kind of people who find these kinds of names (and many other things) fun, and are not put off by it - which is fine. A Computer Science portal for geeks. 10, you had to resort to various tricks such as using Perl code in (??{}) sequences. One of the most useful features of Perl regexes is the backreference, which allows you to recall and use data from your Find regex with your Replace regex. That's because in each iteration of the loop, the current string is placed in $_, and is used by default by print. Perl garbage collector frees programmer from memory management … until the programmer creates circular references. The Greek form, Margaret, is more popular and has been used for centuries, while Pearl was used only in the late Victorian era. 8247 Vapers. regexpr and gregexpr do too, but return more detail in a different format. We will learn what it is, how it is used, and some of its advantages. Join today to get access to thousands of courses. As a valued partner and proud supporter of MetaCPAN, StickerYou is happy to offer a 10% discount on all Custom Stickers, Business Labels, Roll Labels, Vinyl Lettering or Custom Decals. Assigning to a variable, but then never using it, or using a variable once without assigning any value to it ever, are rarely correct in any code. DESCRIPTION. Why is it used? Generally, Perl reads data from a file which in the Perl program can be accessed using open and readline functions. The cookie is a small file embedded on the user's computer. • Perl is very efficient in TEXT and STRING manipulation i. Which is not the commonly used programming language for AI? a) PROLOG b) Java c) LISP d) Perl e) Java script. Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency. Perl comes with a wide selection of builtin functions. `When a class implements an interface, it can be used through a reference to that interface. #!/usr/local/bin/perl This line instructs the operating system running the Perl script on where the executable for Perl and its associated files are located. Perl is everywhere: it's used in system administration, network programming, and graphics programming. It is a high-level programming language written by Larry Wall, specially designed for processing text. Often software is used to extend and regularise ("whiten") their output. Strawberry Perl: A 100% Open Source Perl for Windows that is exactly the same as Perl everywhere else; this includes using modules from CPAN, without the need for binary packages. Perl has an extensive test framework and tools to test any application regardless of the language that was used for the application. Michael Stevenson and Mike Bursell describe how Perl’s design made it ideal for the early web. Linux, Perl, MySQL, git Cloudbeds is one easy-to-use hospitality management suite that simplifies the working lives of hoteliers and hosts. Take this introductory Perl course to see for yourself. Other languages are grim, sterile, cold-war era, industrial Marxist labor camps and slag mines. (By the way, this quoting automatically gets turned off when the delimiter character is encountered). (In fact, the routines are derived (distantly) from Henry Spencer's freely redistributable reimplementation of the V8 routines. "POSIX-compliant unix-like systems" includes a plethora of available OSes including but not limited to Linux, Sun Solaris, BSD, and Mac OS X. Sharepoint throws: A supported MIME type could not be found that matches the content type of the response. United States - Warehouse. Tags: Perl/mod_perl, Moose, TDD, SOA, Postgres, Apache, Xapian, beanstalkd, linux, javascript Pickl was designed to make buying gifts for people easier. This document describes the version of SAX used by Perl modules. at the head of a script tells your system that this file is a set of commands to be fed to the command interpreter indicated. Perl Defined. Since the interpreter actually does convert the program into byte code before executing it, it is sometimes called an interpreter/compiler. A copy of the above was added to the main IM documentation at Introduction to Motion Picture Formats. The name of the 'package' inside. The Basic Local Alignment Search Tool (BLAST) finds regions of local similarity between sequences. See the whole article: Perl DBI and Oracle. There used to be two ways of doing this: setting up callback handlers that get invoked when a particular element type is recognized (SAX), or creating an XML document tree and using tree navigation methods to access individual content fragments (DOM). A flexible plugin system which can be used to dynamically add new advanced features ; Screenshots. Hence, Servlets are more commonly used than CGI. ) to develop the application. The system is integrated with a relational database. 24-1build1) [universe] Perl module for creating generic methods. 940 Vape Brands. ` This program defines an interface and two classes that implement it. Before moving to Binding operators let's have a look at building patterns. What is Perl 3. ” “Erlang has been around since 1986. This document describes the differences between the 5. Although awk is a complete pattern scanning and processing language, it is most commonly used as a Unix command-line filter to reformat the output of other commands. The first part of the string printed out when you say perl -v. Portable Perl Newlines Endianness and Number Width Files and Filesystems System Interaction Interprocess Communication (IPC) External Subroutines (XS) Standard Modules Dates and Times Internationalization Style Chapter 26. The Basic Local Alignment Search Tool (BLAST) finds regions of local similarity between sequences. Perl is the President of the United States. Perl stands for P ractical E xtraction and R eporting L anguage. SIP - similar to SWIG but specialised for Python and C++. Oh really? So that's why you came here. It is very similar in structure to the C language. Perl is a good language yes, but easier to read then PHP no. Essential Perl This document is a quick introduction to the Perl language. Before moving to Binding operators let's have a look at building patterns. Instead of writing the code each time these commonly-performed tasks are needed, routines are created and called when these tasks need to be performed. Many of the web servers commonly used on POSIX-compliant unix-like systems are available for Windows too, including the very popular and well-respected Apache web server. All that without using the word 'refactoring' even once. 1, character + “+” means one or more identical characters, for example, / de + F / refers to def, Deef, deeeeef, etc. PERL Path What is the path to PERL (interpreter)? Applications Available in the cPanel Do You Have Any Applications Available for Customers to Use? Bluehost. Perl is especially good at parsing text, so. As of Perl 5. For complex transliterations the tr/// syntax is bad. The Common Data Model (CDM) is an abstract data model for scientific datasets. Perl's design philosophy is expressed in the commonly cited motto "there's more than one way to do it". They are most commonly used in metal buildings, though they sometimes replace closely spaced rafters in wood frame structures. -p file is a pipe-h file is a symbolic link-L file is a symbolic link-S file is a socket-t file (descriptor) is associated with a terminal device This test option may be used to check whether the stdin ([ -t 0 ]) or stdout ([ -t 1 ]) in a given script is a terminal. It's no secret that that's where I've spent most of my time. References are commonly used when you are returning a large object or data structure (for example an array or hash) from a subroutine.