|Home||Switchboard||Unix Administration||Red Hat||TCP/IP Networks||Neoliberalism||Toxic Managers|
May the source be with you, but remember the KISS principle ;-)
Skepticism and critical thinking is not panacea, but can help to understand the world better
Prev | Contents | Next
Split function is one the few Perl functions that have regular expression as an argument. Its purpose is to take a string and convert it to an array or list breaking at points where the first argument (delimiter) specified with the regular expression matches.
The usual syntax for the split function is
list = split (pattern, string_value);
Here, string_value is the string to be split. pattern is a regular expression to be searched for. Again, it is important to understand that a new element is started every time pattern is matched; pattern itself is not included as part of any element serving as a separator between elements.). The resulting list of elements is returned in list.
For example, the following statement breaks the character string stored in $line into elements delimited by ":", and store them into the array @tokens:
@tokens = split (/:/, $line);
You can specify the maximum number of elements of the list produced by split by specifying the maximum as the third argument. For example:
$line = "This:is:a:string"; @tokens = split (/:/, $line, 3);
As before, this breaks the string stored in $line into elements. After two first elements have been created, no more new elements are created. The rest of the string is assigned to the third element of arrays. A In this case, the list assigned to @list is ("This", "is", "a:string").
You can also assign to several scalar variables at once:
$line = "11 12 13 14 15";This splits $line into the list ("11", "12", "13 14 15"). $var1 is assigned 11, $var2 is assigned 12, and $line is assigned "13 14 15". This enables you to assign the "leftovers" to a single variable, which can then be split again at a later time
($var1, $var2, $line) = split (/\s+/, $line, 3);
Splits the string EXPR into a list of strings and returns that list. By default, empty leading fields are preserved, and empty trailing ones are deleted. (If all fields are empty, they are considered to be trailing.)
In scalar context, returns the number of fields found. In scalar and void context it splits into the @_ array. Use of split in scalar and void context is deprecated, however, because it clobbers your subroutine arguments.
If EXPR is omitted, splits the $_ string. If PATTERN is also omitted, splits on whitespace (after skipping any leading whitespace). Anything matching PATTERN is taken to be a delimiter separating the fields. (Note that the delimiter may be longer than one character.)
If LIMIT is specified and positive, it represents the maximum number of fields the EXPR will be split into, though the actual number of fields returned depends on the number of times PATTERN matches within EXPR. If LIMIT is unspecified or zero, trailing null fields are stripped (which potential users of pop would do well to remember). If LIMIT is negative, it is treated as if an arbitrarily large LIMIT had been specified. Note that splitting an EXPR that evaluates to the empty string always returns the empty list, regardless of the LIMIT specified.
A pattern matching the null string (not to be confused with a null pattern // , which is just one member of the set of patterns matching a null string) will split the value of EXPR into separate characters at each point it matches that way. For example:
produces the output 'h:i:t:h:e:r:e'.
As a special case for split, using the empty pattern // specifically matches only the null string, and is not be confused with the regular use of // to mean "the last successful pattern match". So, for split, the following:
produces the output 'h:i: :t:h:e:r:e'.
Empty leading fields are produced when there are positive-width matches at the beginning of the string; a zero-width match at the beginning of the string does not produce an empty field. For example:
produces the output 'h:i :t:h:e:r:e!'. Empty trailing fields, on the other hand, are produced when there is a match at the end of the string (and when LIMIT is given and is not 0), regardless of the length of the match. For example:
produce the output 'h:i: :t:h:e:r:e:!:' and 'hi:there:', respectively, both with an empty trailing field.
The LIMIT parameter can be used to split a line partially
When assigning to a list, if LIMIT is omitted, or zero, Perl supplies a LIMIT one larger than the number of variables in the list, to avoid unnecessary work. For the list above LIMIT would have been 4 by default. In time critical applications it behooves you not to split into more fields than you really need.
If the PATTERN contains parentheses, additional list elements are created from each matching substring in the delimiter.
produces the list value
If you had the entire header of a normal Unix email message in $header, you could split it up into fields and their values this way:
The pattern /PATTERN/ may be replaced with an expression to specify patterns that vary at runtime. (To do runtime compilation only once, use /$variable/o .)
As a special case, specifying a PATTERN of space (' ' ) will split on white space just as split with no arguments does. Thus, split(' ') can be used to emulate awk's default behavior, whereas split(/ /) will give you as many null initial fields as there are leading spaces. A split on /\s+/ is like a split(' ') except that any leading whitespace produces a null first field. A split with no arguments really does a split(' ', $_) internally.
A PATTERN of /^/ is treated as if it were /^/m , since it isn't much use otherwise.
s/^\s+//; @array = split;After this statement executes, @array will be an array of words. Before splitting the string, you need to remove any beginning whitespace. If this is not done, split will create an array element with the whitespace as the first element in the array, and this is probably not what you want.
$line =~ s/^\s+//; @array = split(/\W/, $line);After this statement executes, @array will be an array of words.
@array = split(//);After this statement executes, @array will be an array of characters. split recognizes the empty pattern as a request to make every character into a separate array element.
@array = split(/:/);@array will be an array of strings consisting of the values between the delimiters. If there are repeated delimiters - :: in this example - then an empty array element will be created. Use /:+/ as the delimiter to match in order to eliminate the empty array elements.
$_ = 'AB AB AC'; print m/c$/i
Prev | Up | Contents | Down | Next
Groupthink : Two Party System as Polyarchy : Corruption of Regulators : Bureaucracies : Understanding Micromanagers and Control Freaks : Toxic Managers : Harvard Mafia : Diplomatic Communication : Surviving a Bad Performance Review : Insufficient Retirement Funds as Immanent Problem of Neoliberal Regime : PseudoScience : Who Rules America : Neoliberalism : The Iron Law of Oligarchy : Libertarian Philosophy
War and Peace : Skeptical Finance : John Kenneth Galbraith :Talleyrand : Oscar Wilde : Otto Von Bismarck : Keynes : George Carlin : Skeptics : Propaganda : SE quotes : Language Design and Programming Quotes : Random IT-related quotes : Somerset Maugham : Marcus Aurelius : Kurt Vonnegut : Eric Hoffer : Winston Churchill : Napoleon Bonaparte : Ambrose Bierce : Bernard Shaw : Mark Twain Quotes
Vol 25, No.12 (December, 2013) Rational Fools vs. Efficient Crooks The efficient markets hypothesis : Political Skeptic Bulletin, 2013 : Unemployment Bulletin, 2010 : Vol 23, No.10 (October, 2011) An observation about corporate security departments : Slightly Skeptical Euromaydan Chronicles, June 2014 : Greenspan legacy bulletin, 2008 : Vol 25, No.10 (October, 2013) Cryptolocker Trojan (Win32/Crilock.A) : Vol 25, No.08 (August, 2013) Cloud providers as intelligence collection hubs : Financial Humor Bulletin, 2010 : Inequality Bulletin, 2009 : Financial Humor Bulletin, 2008 : Copyleft Problems Bulletin, 2004 : Financial Humor Bulletin, 2011 : Energy Bulletin, 2010 : Malware Protection Bulletin, 2010 : Vol 26, No.1 (January, 2013) Object-Oriented Cult : Political Skeptic Bulletin, 2011 : Vol 23, No.11 (November, 2011) Softpanorama classification of sysadmin horror stories : Vol 25, No.05 (May, 2013) Corporate bullshit as a communication method : Vol 25, No.06 (June, 2013) A Note on the Relationship of Brooks Law and Conway Law
Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds : Larry Wall : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOS : Programming Languages History : PL/1 : Simula 67 : C : History of GCC development : Scripting Languages : Perl history : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history
The Peter Principle : Parkinson Law : 1984 : The Mythical Man-Month : How to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Haterís Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite
Most popular humor pages:
Manifest of the Softpanorama IT Slacker Society : Ten Commandments of the IT Slackers Society : Computer Humor Collection : BSD Logo Story : The Cuckoo's Egg : IT Slang : C++ Humor : ARE YOU A BBS ADDICT? : The Perl Purity Test : Object oriented programmers of all nations : Financial Humor : Financial Humor Bulletin, 2008 : Financial Humor Bulletin, 2010 : The Most Comprehensive Collection of Editor-related Humor : Programming Language Humor : Goldman Sachs related humor : Greenspan humor : C Humor : Scripting Humor : Real Programmers Humor : Web Humor : GPL-related Humor : OFM Humor : Politically Incorrect Humor : IDS Humor : "Linux Sucks" Humor : Russian Musical Humor : Best Russian Programmer Humor : Microsoft plans to buy Catholic Church : Richard Stallman Related Humor : Admin Humor : Perl-related Humor : Linus Torvalds Related humor : PseudoScience Related Humor : Networking Humor : Shell Humor : Financial Humor Bulletin, 2011 : Financial Humor Bulletin, 2012 : Financial Humor Bulletin, 2013 : Java Humor : Software Engineering Humor : Sun Solaris Related Humor : Education Humor : IBM Humor : Assembler-related Humor : VIM Humor : Computer Viruses Humor : Bright tomorrow is rescheduled to a day after tomorrow : Classic Computer Humor
The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D
Copyright © 1996-2020 by Softpanorama Society. www.softpanorama.org was initially created as a service to the (now defunct) UN Sustainable Development Networking Programme (SDNP) in the author free time and without any remuneration. This document is an industrial compilation designed and created exclusively for educational use and is distributed under the Softpanorama Content License. Original materials copyright belong to respective owners. Quotes are made for educational purposes only in compliance with the fair use doctrine.
FAIR USE NOTICE This site contains copyrighted material the use of which has not always been specifically authorized by the copyright owner. We are making such material available to advance understanding of computer science, IT technology, economic, scientific, and social issues. We believe this constitutes a 'fair use' of any such copyrighted material as provided by section 107 of the US Copyright Law according to which such material can be distributed without profit exclusively for research and educational purposes.
This is a Spartan WHYFF (We Help You For Free) site written by people for whom English is not a native language. Grammar and spelling errors should be expected. The site contain some broken links as it develops like a living tree...
|You can use PayPal to make a contribution, supporting development of this site and speed up access. In case softpanorama.org is down you can use the at softpanorama.info|
Last modified: March 12, 2019