DGerman's adaptation of Rex Swain's HTMLified Perl 5 Reference Guide _

`fixed`	denotes literal text.	`word`	is a keyword, i.e., a word with a special meaning.
`THIS`	means variable text, i.e., things you must fill in.	`RETURN key`	denotes pressing a keyboard key.
`THIS^£`	means that `THIS` will default to `$_` if omitted.	[…]	denotes an optional part.

Quoting:

`'abc'` except `\'` and `\\`	No $variable or escape sequences intreptation `print 'This will NOT output the $answer';`
`q/abc/` Almost any pair of delimiters can be used instead of `/`…`/`.
`"abc"`	$variables are intrepreted and escape sequences are processed. `print "The answer is $answer \n";`
`qq/abc/`.
``command``	evaluates to the output of the `command.`
`qx/command/`.

Escape sequences:

\t

\n

\r

\f

\b

\a

\033

\x1b

\e

\c[

\l

\u

\L

\U

\E

\Q

\E

Literals

Numeric: 123, 1_234^†, 1.234, 5E-10, 0xff (hex), 0377 (leading zero implies octal)

Variables

`$var`	simple scalar
`$var[28]`	29th element of array `@var`.
`$p = \@var`	now `$p` is a reference to array `@var`.
`$$p[28]` `$p->[28]`	29th element of array referenced by `$p`.
`$var[-1]`	last element of array `@var`.
`$var[$i][$j]`	`$j`th element of the `$i`th element of array `@var`.
`$#var`	last index of array `@var`.
`@var`	the entire array. In a scalar context, the number of elements in the array.
`@var[3,4,5]`	a slice of array `@var`.
`@var{'a','b'} ($var{'a'},$var{'b'})`	a slice of `%var`;
`%var`	the entire hash. In a scalar context, `true` if the hash has elements.
`$var{'Feb'}`	a value from hash `%var`.
`$p = \%var`	now `$p` is a reference to hash `%var`
`$p->{'Feb'}`. `$$p{'Feb'}`	a value from hash referenced by `$p`
`$var{'a',1,`…`}`	emulates a multidimensional array.
`('a'`…`'z')[4,7,9]`	a slice of an array literal.
`PKG::var`	a variable from a package, e.g., `$pkg::var`, `@pkg::ary`.
`\OBJECT`	reference to an object, e.g., `\$var`, `\%hash`.
`*NAME`	refers to all objects represented by `NAME`. `n1 = n2` makes `n1` an alias for `n2`. `*n1 = $n2` makes `$n1` an alias for `$n2`.

Array

@values(1, 2, 3)
@values(1..4) aka @values(1,2,3,4)
@values('a'..'z')
@values qw/foo bar …/ is the same as

('foo','bar',…).

Array reference

$value[1,2,3]

Hash

(associative array)

initalze:
%myhash(KEY1,val1, KEY2,val2,…)
Also
%myhash(KEY1=>val1, KEY2=>val2,…)

reference:

$myhash{KEY1,val1, KEY2,val2,…}

Use a {block} to return the correct type of reference instead of the variable identifier,
Example: ${…},
&{…}.
$$p is a shorthand for ${$p}.

Operators

`**`		Exponentiation
`+ - * /`		Addition, subtraction, multiplication, division
`%`		Modulo division i.e. remainder
`& \| ^`		Bitwise AND, OR, exclusiveOR
`>>`	`<<`	Bitwise shift right, left
`\|\|`	`&&`	Logical OR, AND
`.`		string Concatenation
`x`		left operand (an array or a string) repeated the number of times specified right operand
All of the above operators also have an assignment operator, e.g., `.=`

`->`		Dereference operator
`\`		Reference (unary)
`!`	`~`	Negation (unary), bitwise complement (unary)
`++`	`--`	Auto-increment (magical on strings), auto-decrement
Logical operators return 1 for true ( So don't use $xxPresent=true; )
Numeric			String
`==`	`!=`	equality, inequality	`eq`	`ne`
`<`	`>`	less than, greater than	`lt`	`gt`
`<=`	`>=`	less (greater) than or equal to	`le`	`ge`
`<=>`		compare. Returns -1, 0, 1.	`cmp`
`=~`	`!~`	negate Search pattern, substitution, or translation
`..`		Range (scalar context) , enumeration (array context)
`?:`		Alternation (if-then-else)
`,`		Comma operator, also list element separator.
`=>`		Comma operator, also list element separator.
`not`		Low-precedence negation
`and`		Low-precedence AND
`or`	`xor`	Low-precedence OR, exclusiveOR

All functions can be used as list operators, in which case they have very high or very low precedence, depending on whether you look at the left or the right side of the operator.
Operators not, and, or and xor have lower precedence.

A "list" is a list of expressions, variables, or lists.
An array variable or an array slice may be used instead of a list.

Parentheses clarify precedence.

Statements

A statement is an expression, optionally followed by a modifier, terminated by a semicolon.
The semicolon may be omitted if the statement is the final one in a block.

Statements combined form a block when enclosed in {}.

Execution of expressions can depend on other expressions using a modifier.

expr1

if

expr2

;

expr1

unless

expr2

;

expr1

unless

expr2

;

expr1

while

expr2

;

do

block

while

expr

;

do

block

until

expr

;

Conditional execution: logical operators

expr1

||

expr2

;

expr1

2|

expr2

;

expr1

?

expr2

:

expr3

;

if (expr) block

[

elsif (expr) block

]

else block

]

unless (expr) block

[

else

block

]

[

label

:

]

while

(expr)

block

[

continue

block

]

[

label

:

]

until

(expr)

block

[

continue

block

]

[

label

:

]

for (expr; expr; expr) block

[

label

:

]

foreach var

^£

list

block

[

label

:

]

block

[

continue

block

]

Program flow can be controlled with:

`goto` `label`
`last` [ `label` ]	Immediately exits the loop in question. Skips continue block.
`next` [ `label` ]	Starts the next iteration of the loop.
`redo` [ `label` ]	Restarts the loop block without evaluating the conditional again.

which are guaranteed to perform block once before testing expr, and

do

block

which turns block into an expression.

Subroutines, Packages and Modules

do f, require f, or use f

sub name { @arrayOfAllArgs aka @_; $firstArg aka $_[1]; $_[2] aka xxx;… ; statments; return }

`&SUBROUTINE LIST`	Executes a `SUBROUTINE` declared by `sub` , and returns the value of the last expression evaluated in `SUBROUTINE`. `SUBROUTINE` can be an expression yielding a reference to a code object. The `&` may be omitted if the subroutine has been declared before being used.
[`sub] BEGIN { expr; … }`	Defines a setup `block` called before execution.
[`sub] END { expr; … }`	Defines a cleanup `block` called prior to termination.
`sub name { expr`; … }	Designates `name` as a subroutine. Parameters are passed by reference as array `@_`. Returns the value of the last expression evaluated.
`bless ref` [`,package`]	Turns the object `ref` into an object in `package.` Returns the reference.
`caller` [`expr`]	Returns an array (`$`package,`$`file,`$`line,…) for a specific subroutine call. `caller` returns this info for the current subroutine, `caller(1)` for the caller of this subroutine, etc. Returns `false` if no caller.
`do subroutine list`	Deprecated form of `&subroutine.`
`goto` `&subroutine`	Substitutes a call to `subroutine` for the current subroutine.
`return expr`
`tie var, package, [list]`	Can be used to bind a dbm or ndbm file to a hash. example: `BEGIN { @AnyDBM_File::ISA = qw(DB_File GDBM_File NDBM_File SDBM_File); } use AnyDBM_File ; tie %fin, "AnyDBM_File",$filein, O_RDWR, 0600 or die "Cannot open:\"$ts\" $! \n";` If `O_RDONLY` assignments fail without warning! (example:`$fin{$key}="0909";`)
`untie var`	Breaks the binding between the variable and the package.

`require expr^£`	If `expr` is numeric, requires Perl to be at least that version. Otherwise `expr` must be the name of a file that is included from the Perl library. Does not include more than once, and yields a fatal error if the file does not evaluate to a `true` value. If `expr` is a bare word, assumes extension `.pm` for the name of the file.
`import module` [ [`version`] `list` ]
`no module` [ `list` ]	Cancels imported semantics. See `use`.
`use MODULE [ [VERSION] list ]`	Imports semantics from the named module into the current package.
`package name`	Designates the remainder of the current block as a package.

Code reference:

sub {STATEMENTS}

fhs:

STDIN, STDOUT, STDERR, ARGV, DATA.
User-specified: HANDLE, $var.

Globs:

<pattern> evaluates to all filenames according to the pattern. Use <${var}> or glob $var to glob from a variable.

Here-Is:
<<identifier
Shell-style "here document."

Special tokens:
__FILE__: filename;
__LINE__: line number;
__END__: end of program;
remaining lines can be read using the fh DATA.

Object-Oriented Programming

Perl rules of object oriented programming:

An object is simply a reference that happens to know which class it belongs to. Objects are blessed, references are not.
A class is simply a package that happens to provide methods to deal with object references. If a package fails to provide a method, the base classes as listed in @ISA are searched.
A method is simply a subroutine that expects an object reference (or a package name, for static methods) as the first argument.

Methods can be applied with:

METHOD

OBJREF

PARAMETERS

OBJREF

->

METHOD

PARAMETERS

Arithmetic Functions

use List::Util qw(

 reduce any all none notall first max maxstr min minstr product sum sum0

      pairs unpairs pairkeys pairvalues pairfirst pairgrep pairmap shuffle uniq uniqnum uniqstr

    );

`exp` `expr^£`	`e` ^expr	`sin` `expr^£`	sine in radians
`log` `expr^£`	natural logarithm (base `e`)	`cos` `expr^£`	cosine in radians
`sqrt` `expr^£`	square root	`atan2 y,x`	arctangent of `y/x` in the range -π to π.
`min(list) max(list) avg(list)`	`use List::Util qw[min max];`
`abs` `expr^£`	absolute value
`int` `expr^£`	integer portion
`rand` [ `expr` ]	random fractional number between 0 and `expr`. default: between 0 and 1.	`srand` [ `expr` ]	seed for `rand`

`time`	seconds since January 1, 1970. Suitable for `gmtime` and `localtime`.

Conversion Functions

localtime expr^£ Converts a time as returned by the time function to ctime(3) string.
Sun Aug 15 20:26:21 2010

In array context, returns a 9-element array with the time analyzed for the local time zone.
$mon has the range 0..11 and $wday has the range 0..6.
($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time); ## for display and log name $month=(January,February,March,April,May,June,July,August,September,October,November,December)[$mon]; if ($mday< 10) { $mday= "0$mday" }; if (++$mon< 10) { $mon= "0$mon" }; $year = 1900 + $year; if ($hour< 10) { $hour= "0$hour" }; if ( $min< 10) { $min= "0$min" }; if ( $sec< 10) { $sec = "0$sec" }; xx

gmtime expr^£ Converts a time as returned by the time function to a 9-element array Greenwich

chr expr^£ Returns the character represented by the decimal value expr.
hex expr^£ Returns the decimal value of expr interpreted as a hex string.
oct expr^£ Returns the decimal value of expr interpreted as an octal string.
exprs begining with 0x are intrepreted as hexidecimal. ord expr^£ Returns the ASCII value of the first character of expr.

vec expr, offset, bits Treats string expr as a vector of unsigned integers, and yields the bit at offset. bits must be between 1 and 32. May be assigned to.

Structure Conversion

`pack` `template,` `list`	Packs the values into a binary structure using `template`.
`unpack` `template,` `expr`	Unpacks the structure `expr` into an array, using `template`.

TEMPLATE is a sequence of characters as follows:

`a`	`A`	ASCII string, null-	space-padded
`b`	`B`	Bit string in ascending	descending order
`c`	`C`	Native	unsigned char value
`f`	`d`	Single	double float in native format
`h`	`H`	Hex string, low	high nybble first
`i`	`I`	Signed	unsigned integer value
`l`	`L`	Signed	unsigned long value
`n`	`N`	Short	long in network (big endian) byte order
`s`	`S`	Signed	unsigned short value
`u`	`P`	Uuencoded string	pointer to a string
`v`	`V`	Short	long in VAX (little endian) byte order
`x`	`@`	Null byte	null fill until position
`X`		Backup a byte

Character may be followed by a decimal repeat count; an asterisk (*) specifies all remaining arguments.
If the format is preceded with %N, unpack returns an N-bit checksum instead.
Spaces may be included in the template for readability purposes.

String Functions

`chomp list^£`	Removes line endings from all elements of the list. Returns total number of characters removed.
`chop list^£`	Chops off the last character on all elements of the list. Returns last chopped character.
`crypt plaintext, salt`	Encrypts a string.
`eval expr^£`	`expr` is parsed and executed as if it were a Perl program. Returns value of the last expression evaluated. If there is a syntax error or runtime error, an undefined string is returned by `eval`, and `$@` error message. See `eval` Miscellaneous.
`index str, substr[, offset ]`	position of the first `substr` in `str` at or after `offset`₀ . If the `substr` is not found, returns `-1`
`rindex str, substr[, offset]`	position of the last `substr` in `str` at or before `offset`₀.( reverse index)
`length expr^£`	length in characters of value of `expr`.
`quotemeta expr`	regular expression metacharacters quoted.
`substr expr,` ±`offset`₀ [,`len`] [,`repl`]	substring of length `len` from `expr`. If `offset`₀ is negative, counts from the end of the string. May be assigned to.

`lc expr`	lowercase
`lcfirst expr`	first character lowercase.
`uc expr`	UPPERCASED
`ucfirst expr`	First character Uppercased.

Array and List Functions

See use List::Util qw(first max maxstr min minstr reduce shuffle sum);

`delete` `$HASH{KEY}`	Deletes value from the hash at `KEY`. Returns the deleted value unless `HASH` is tied to a package that does not support this.
`each` `%HASH`	Returns a 2-element array consisting of the key and value for the next value of the hash. Entries are returned in an unpredictable order. After all values have been returned, a null array is returned. The next call to `each` restarts iteration.
`exists expr^£`	Checks if the specified key exists in its hash array.
`grep expr, list grep block list`	Evaluates `expr` or `block` for each element of the `list`, locally setting `$_` to refer to the element. Modifying `$_` will modify the corresponding element from `list`. Returns the array of elements from `list` for which `expr` returned `true`.
`join expr, list`	Joins the separate strings of `list` into a single string with fields separated by the value of `expr`, and returns the string.
`keys` `%HASH`	Returns an array of the keys of `HASH`.
`map expr, list map BLOCK LIST`	Evaluates `expr` or `block` for each element of the `list`, locally setting `$_` to refer to the element. Modifying `$_` will modify the corresponding element from `list`. Returns the list of results.
`pop` `@ARRAY`	Pops off and returns the last value of the array.
`push` `@ARRAY, list`	Pushes the values of `list` onto the end of the array.
`reverse` `list`	In array context, returns the `list` in reverse order. In scalar context: returns the first element of `list` with bytes reversed.
`scalar` `@ARRAY`	Returns the number of elements in the array.
`scalar` `%HASH`	Returns a `true` value if the hash has elements defined.
`shift` [ `@ARRAY ]`	Shifts the first value of the array off and returns it, shortening the array by 1 and moving everything down. If `@ARRAY` is omitted, shifts `@ARGV` in main and `@_ in subroutines.`
`sort` [ `SUBROUTINE` ] `list`	Sorts the `list` and returns the sorted array value. `SUBROUTINE`, if specified, must return less than zero, zero, or greater than zero, depending on how the elements of the array (available to the routine as `$a` and `$b`) are to be ordered. `SUBROUTINE` may be the name of a user-defined routine, or a `block`.
`splice` `@ARRAY, offset [ , LENGTH [ , list ] ]`	Removes the elements of `@ARRAY` designated by `offset` and `LENGTH`, and replaces them with `list` (if specified). Returns the elements removed.
`split` [ `pattern` [ `, expr^£ [ , LIMIT ] ] ]`	Splits a string into an array of strings, and returns it. If `LIMIT` is specified, splits into at most that number of fields. If `pattern` is also omitted, splits at the whitespace. If not in array context, returns number of fields and splits to `@_`. See also Search and Replace.
`unshift` `@ARRAY, list`	Prepends list to the front of the array, and returns the number of elements in the new array.
`values` `%HASH`	Returns a normal array consisting of all the values of the named hash.

Regular Expressions

Each character matches itself, except + ? . * ^ $ ( ) [ ] { } | \.
The special meaning of these characters is escaped using a \.

Quantified subpatterns match as many times as possible.
When followed with a ? they match the minimum number of times.

These are the quantifiers:

. matches any character, but not a newline unless it is a single-line match (see m//s).

(…) groups a series of pattern elements to a single element.

^ matches the beginning of the target.
In multiline mode (see m//m) also matches after every newline character.

$ matches the end of the line.
In multiline mode also matches before every newline character.

[ … ]

denotes a class of characters to match.

`alpha`	alphabetical `[A-Za-z]`
`alnum`	alphanumeric character. `[A-Za-z0-9]`
`ascii`	character in the ASCII character set.
`blank`	equal to a space or a horizontal tab ("\t"). GNU extension,
`cntrl`	control character.
`digit`	decimal digit ("[0-9]"), equivalent to "\d".
`graph`	printable , i.e. graphic. excludes space.
`print`	printable ,including a space
`punct`	graphical excluding "word" characters. Note [5].
`space`	whitespace . "\s" plus the vertical tab ("\cK").
`lower`	`[a-z]`
`upper`	`[A-Z]`
`word`	`[A-Za-z0-9_]`, equivalent to `\w` Perl extension
`xdigit`	hexadecimal digit `[0-9a-fA-F]`

[^ … ] negates the class.

( … | … | … ) matches one of the alternatives.

(?# comment )

(?: REGEXP ) does not make back-references.

(?= REGEXP ) Zero width positive look-ahead assertion.

(?! REGEXP ) Zero width negative look-ahead assertion.

(? MODIFIER )

Embedded pattern-match modifier. MODIFIER can be one or more of i, m, s, or x.

i igore case
x extension

+ matches the preceding pattern element one or more times.

? matches zero or one times. i.e. not more than one.

* matches zero or more times.

{N,M} at least N and no more than M matchs ( do not escape the { as with a command like grep)

{N} means exactly N times

{N,} at least N times.

A \ escapes special meaning of the following character if non-alphanumeric,
A \ Introduces special usage for:

\w matches alphanumeric, including _, \W matches non-alphanumeric.

\s matches whitespace, \S matches non-whitespace.

\d matches digit, \D matches non-digit.

\A \Z matches the beginning of the string, \Z matches the end.

\b matches word boundaries, \B matches non-boundaries.

\G Go on where the previous m//g search left off.

\n Newline

\r Return

\f Formfeed

\t Tab

\w, \s and \d may be used within character classes, \b denotes backspace in this context.

Back-references:

\1 … \9 refer to matched subexpressions, grouped with (), inside the match.

\10 and up can also be used if the pattern matches that many subexpressions.

Variables local to the current block:
$`	string preceding
`$&`	string matched by the last successful pattern match.
`$'`	string following
`$+`	last bracket matched by the last search pattern.
`$1`…$9… `$10`… and up (only available if Contain subpatterns from the corresponding sets of parentheses in the last pattern successfully matched.)

match contained that many subpatterns.

With modifier x, whitespace can be used in the patterns for readability purposes.

Search (Match) and Replace

[`expr =~` ] [`m`] `/pattern/` [`g`][`i`][`m`][`o`][`s`][`x`]	Matches `expr` (default: `$_`) for `pattern`. Leading `m` permits use of alternate of delimiters. In array context, an array is returned consisting of the subexpressions matched by the parentheses in the pattern, `g` global matches as many times as possible `i` ignores case `o` intreprets `$variables` only once. `m` treats the string as multiple lines `s` treats the string as a single line `x` allows for regular expression extensions. (ignore whitespace, allow `#` comments) If `pattern` is empty, the most recent pattern from a previous match or replacement is used. With `g` the match can be used as an iterator in scalar context.
`pos scalar`	Returns the position where the last `m/…/g` search left off
`?pattern?`	matches only once between calls to the `reset` operator.
[`$var =~` ] `s/pattern/subs/` [`e`][`g`][`i`][`m`][`o`][`s`][`x`]	substitues `subs` for `pattern` in `$var`. Returns the number of substitutions or false. `e` evaluates `subs` as a Perl expression `g` replaces all occurrences of `pattern` Almost any delimiter may replace the slashes (helpful if strings contain slashes, using `\|` looks nice ed ) If `'` (apostrophes) are delimiters, no interpretation of `$variables`. If bracketing delimiters ( `( ), [ ], { }, < >` ) are used, `pattern` and `subs` may have their own delimiters, For example: `$ary2fun =~s(@arrayn[.])[functn()]`. If `pattern` is empty, the most recent pattern from a previous match or replacement is used. for example: `$x= 'xyz1aaa788899ccc' ; $x =~ s/xyz([[:digit:]])aaa(.)ccc/DIGITS ARE ^†$1 $2/; print "$x \n"; DIGITS ARE 1 788899`
[`$var` `=~`] `tr/chars/replchars/` [`c`][`d`][`s`]	Translates all occurrences of `chars` to the corresponding character in `replchars`. `y` may be used instead of `tr`. Returns the number of characters replaced. `c` complements the `SEARCHLIST` `d` deletes all characters found in `SEARCHLIST` that do not have a corresponding character in `replchars` `s` squeezes all sequences of characters that are translated into the same target character into one occurrence of this character. for `scalar`. May be assigned to.
`study $var^£`	Study the scalar variable `$var` in anticipation of performing many pattern matches on its contents before the variable is next modified.

File Test Operators

These unary operators takes one argument (or $_), filename or fh.
If the special argument _ (underscore) is passed, information is from the preceding test or stat .

`-r -w -x`	readable/writable/executable by effective uid/gid.
`-R -W -X`	readable/writable/executable by real uid/gid.
`-o -O`	owned by effective/real uid.
`-e -z`	exists/has zero size.
`-s`	exists and has non-zero size. Returns the size.
`-f -d`	a plain file/ directory.
`-l -S -p`	a symbolic link/ socket/ named pipe (FIFO).
`-b -c`	a block/character special file.
`-u -g -k`	setuid/setgid/sticky bit set.
`-t`	fh (`STDIN` by default) is opened to a tty.
`-T -B`	text/non-text (binary) file. Return `true` on a null file, or a file at EOF when testing a fh.
`-M -A -C`	File modification / access / inode-change time. Measured in days. Value returned reflects the file age at the time the script started. See also `$^T` Special Variables.

File Operations

Functions operating on a list of files return the number of files successfully operated upon.

`chmod` `list`	Changes the permissions of a list of files. The first element of the list must be the numerical mode.
`chown` `list`	Changes the owner and group of a list of files. The first two elements of the list must be the numerical uid and gid.
`truncate` `file,size`	Truncates `file` to`size`. `file` may be a filename or a fh.
`mkdir` `DIR,` `MODE`	makes a directory with given permissions.(MODE) Sets `$!`
`rmdir` `filename^£`	removes the directory if it is empty. Sets `$!`
`stat` `file`	Returns: (`$`dev, `$`ino, `$`mode, `$`nlink, `$`uid, `$`gid, `$`rdev, `$`size, `$`atime, `$`mtime, `$`ctime, `$`blksize, `$`blocks).
`lstat` `file`	Like `stat`, but does not traverse a final symbolic link. `file` can be a fh, an expression evaluating to a filename, or `_` to refer to the last file test operation or `stat` call. Returns a null list if the `stat` fails.
`rename oldname,newname`
`link` `symlink oldfile, newfile`	see `ln`
`readlink` `expr^£`	Returns the value of a symbolic link.
`unlink` `list`	Deletes a list of files.
`utime` `list`	Changes the access and modification times. The first two elements of the list must be the numerical access and modification times.

Input / Output

A file handle:fh may be

omitted which uses stdin | stdout
predefined (e.g., STDOUT) ,
opened by open
or a scalar variable that evaluates to the name of a fh .

< > Reads from the input stream formed by the files specified in @ARGV, or standard input

<fh> In scalar context, reads a single line from the file on fh.
In array context, reads the whole file.

open fh [ , [mode]filename ]

Opens a file and associates it with fh.
If filename is omitted, the scalar variable named fh contains the filename.
mode prefixes :

`<`or omitted	input
`>`	output, creating it if necessary.
`>>`	append mode.
`+<`	with read/write access (file must exist).
`+>`	with read/write access (file truncated).

or instead of filename

`\|cmd`	opens a pipe to command `cmd`; forks if `cmd` is `-`.
`cmd\|`	opens a pipe from command `cmd`; forks if `cmd is -.`

If filename is &fh the new fh is connected to the (previously opened) fh

If filename is &=N, file will be connected to the file descriptor n.

open returns undef upon failure, true otherwise.

close fh Closes the file or pipe

print [ fh ] [ list^£ ] Equivalent to print fh sprintf list.

printf[([fh] list^£)] Equivalent to print fh sprintf(list). as with printf
Templates for formating

read fh, $var, length [ , offset ] Reads LENGTH binary bytes from the file into the variable at offset. Returns number of bytes actually read.

getc [ fh ] returns the next character from the file, or an empty string on end of file.

seek fh, POSITION, WHENCE positions the file. Returns true if successful. wence

eof fh Returns true if the next read will return end of file, or if the file is not open.

eof Returns the EOF status for the last file read.

eof() Indicates EOF on the pseudo file formed of the files listed on the command line.

fcntl fh, FUNCTION, $var Implements the fcntl(2) function. This function has non-standard return values.

fileno fh Returns the file descriptor for a given (open) file.

flock fh, operation Calls filelock on the file. operation sum of 1 (shared), 2 (exclusive), 4 (non-blocking), or 8 (unlock).

ioctl fh, FUNCTION, $var Performs >ioctl(2) on the file. This function has non-standard return values.

pipe readhandle, writehandle Returns a pair of connected pipes.

select [ fh ] Returns the currently selected fh. Sets the current default fh for output operations if fh is supplied.

select RBITS, WBITS, NBITS, TIMEOUT Performs a select(2) system call with the same parameters.

sprintf format, list Returns a string formatted as with printf

sysread fh, $var, LENGTH [ , offset ] Reads LENGTH bytes into $var at offset.

syswrite fh, SCALAR, LENGTH [ , offset ] Writes LENGTH bytes from SCALAR at offset.

tell [ fh ] Returns the current file position for the file. If filename is omitted, assumes the file last read.

write [ fh ] Writes a formatted record to the specified file, using the format associated with that file.

binmode fh the file to be read or written in binary mode as opposed to text mode (null operation on UNIX).

dbmopen %HASH, Deprecated, use tie instead.

dbmclose %HASH Deprecated, use untie instead.

Formats

formline PICTURE, list
Formats list according to PICTURE and accumulates the result into $^A.

write [ fh ]
Writes a formatted record to the specified file, using the format associated with that file.

Formats are defined as:

format

NAME

=

FORMLIST

.

FORMLIST pictures the lines, and contains the arguments which will give values to the fields in the lines. NAME defaults STDOUT

Picture fields are:

`@<<<`…	left adjusted field, repeat the `<` to denote the desired width
`@>>>`…	right adjusted field
`@\|\|\|`…	centered field
`@#.##`…	numeric format with implied decimal point
`@*`	a multi-line field

Use ^ instead of @ for multiline block filling.
Use ~ at the beginning of a line to suppress unwanted empty lines.
Use ~~ at the beginning of a line to have this format line repeated until all fields are exhausted.
Use $- to zero to force a page break on the next write.
See $^, $~, $^A, $^F, $- and $= Special Variables.

Directory Reading Routines

`opendir` `DIRHANDLE,` `DIRNAME`	Opens a directory on the handle specified.
`closedir` `DIRHANDLE`	Closes a directory opened by `opendir`.
`readdir` `DIRHANDLE`	Returns the next entry (or an array of entries) from the directory.
`rewinddir` `DIRHANDLE`	Positions the directory to the beginning.
`seekdir` `DIRHANDLE,` `pos`	Sets position for `readdir` on the directory.
`telldir` `DIRHANDLE`	Returns the position in the directory.

System Interaction

`alarm secs`	Schedules a `SIGALRM` to be delivered after `secs` seconds.
`chdir [ expr ]`	Changes the working directory. Uses `$ENV{"HOME"}` or `$ENV{"LOGNAME"}` if `expr` is omitted.
`chroot filename^£`	Changes the root directory for the process and its children.
`die [ list ]`	Output `list at line n` to `STDERR` and exits with the current value of `$!` (errno). If `$!` is 0, exits with the value of `($? >> 8)`. 255 If `($? >> 8)` is 0. `list` defaults to "`Died`".
`warn [ list ]`	Output `list at programName line #` on `STDERR` defaults "`Warning: something's wrong`".
`exec list`	Executes the system command in `list`; does not return.
`system list`	Executes the system command in `list` as `exec list` except that a fork is performed first, and the parent process waits for the child process to complete.
`syscall util, arg1, …`
`exit [ expr ]`	Exits immediately with the value of `expr`, which defaults to `0` (zero). 9 if the compilation failed. Calls `END` routines and object destructors before exiting.
`fork`	Does a `fork`(2) system call. Returns the process ID of the child to the parent process and zero to the child process.
`getlogin`	Returns the current login name as known by the system.
`getpgrp [ pid ]`	Returns the process group for process `PID` (0, or omitted, means the current process).
`getppid`	Returns the process ID of the parent process.
`getpriority which, who`	Returns the current priority for a process, process group, or user.
`glob` `pat`	Returns a list of filenames that match the shell pattern `PAT`.
`kill` `list`	Sends a signal to a list of processes. The first element of the list must be the signal to send (either numeric, or its name as a string).
`setpgrp` `PID,` `PGRP`	Sets the process group for the `PID` (0 means the current process).
`setpriority WHICH, WHO, PRIORITY`	Sets the current priority for a process, process group, or a user.
`sleep` [ `secs` ]	if no argument, waits for signal. Returns seconds actually slept.( `usleep()`
`times`	Returns a 4-element array (0: `$`user, 1: `$`system, 2: `$`cuser, 3: `$`csystem) user and system times, in seconds, for this process and the children of this process.
`umask` [ `expr` ]	Sets the umask for the process and returns the old one. If `expr` is omitted, returns current umask value.
`wait`	Waits for a child process to terminate and returns the process ID of the deceased process (-1 if none). The status is returned in `$?` ( `$?` is NOT the return of operations like `s//` (substitute).
`waitpid` `PID,` `FLAGS`	Performs the same function as the corresponding system call.

Networking

`accept` `NEWSOCKET,` `GENERICSOCKET`	Accepts a new socket.
`bind` `SOCKET,` `NAME`	Binds the `NAME` to the `SOCKET`.
`connect` `SOCKET,` `NAME`	Connects the `NAME` to the `SOCKET`.
`getpeername` `SOCKET`	Returns the socket address of the other end of the `SOCKET`.
`getsockname` `SOCKET`	Returns the name of the `SOCKET`.
`getsockopt` `SOCKET,` `LEVEL,` `OPTNAME`	Returns the socket options.
`listen` `SOCKET,` `QUEUESIZE`	Starts listening on the specified `SOCKET`.
`recv` `SOCKET,` `SCALAR,` `LENGTH,` `FLAGS`	Receives a message on `SOCKET`.
`send` `SOCKET,` `MSG,` `FLAGS` [ `,` `TO` ]	Sends a message on the `SOCKET`.
`setsockopt` `SOCKET,` `LEVEL,` `OPTNAME,` `OPTVAL`	Sets the requested socket option.
`shutdown` `SOCKET,` `HOW`	Shuts down a `SOCKET`.
`socket` `SOCKET,` `DOMAIN,` `TYPE,` `PROTOCOL`	Creates a `SOCKET` in `DOMAIN` with `TYPE` and `PROTOCOL`.
`socketpair` `SOCKET1,` `SOCKET2,` `DOMAIN,` `TYPE,` `PROTOCOL`	Creates a pair of bidirectional sockets.

System V IPC

You need to require "sys/ipc.ph" before you can use the symbolic names of the operations.

`msgctl` `ID,` `CMD,` `ARGS`	Calls `msgctl`(2). If `CMD` is `&IPC_STAT` then `ARGS` must be a variable.
`msgget` `KEY,` `FLAGS`	Creates a message queue for `KEY`. Returns the message queue identifier.
`msgsnd` `ID,` `MSG,` `FLAGS`	Sends `MSG` to queue `ID`.
`msgrcv` `ID,` `$var,size,` `TYPE,` `FLAGS`	Receives a message from queue `ID` into `var`.
`semctl` `ID,` `SEMNUM,` `CMD,` `arg`	Calls `semctl`(2). If `CMD` is `&IPC_STAT` of `&GETALL` then `arg` must be a variable.
`semget` `KEY,` `NSEMS,size,` `FLAGS`	Creates a set of semaphores for `KEY`. Returns the message semaphore identifier.
`semop` `KEY,` …	Performs semaphore operations.
`shmctl` `ID,` `CMD,` `arg`	Calls `shmctl`(2). If `CMD` is `&IPC_STAT` then `arg` must be a variable.
`shmget` `KEY,size,` `FLAGS`	Creates shared memory. Returns the shared memory segment identifier.
`shmread` `ID,` `$var,` `pos,size`	Reads at most`size` bytes of the contents of shared memory segment `ID` starting at offset `pos` into `var`.
`shmwrite` `ID,` `STRING,` `pos,size`	Writes at most`size` bytes of `STRING` into the contents of shared memory segment `ID` at offset `pos`.

Miscellaneous

`defined` `expr`	Tests whether the lvalue `expr` has an value.
`undef` [ `lvalue` ]	Undefines the `lvalue`. Always returns the undefined value.
`do` `filename`	Executes `filename` as a Perl script. See also `require` Subroutines, Packages and Modules.
`dump` [ `label` ]	core dump, contiune at `label`.
`eval` `{` `expr` `;` … `}`	Executes the code between `{` and `}`. Traps runtime errors as described with `eval(expr)`, in the section String Functions.
`local` `variable`
`local` `(` `list` `)`	Creates a scope for the listed variables local to the enclosing block, subroutine or `eval`.
`my` `variable`
`my` `(` `list` `)`	Creates a scope for the listed variables lexically local to the enclosing block, subroutine or `eval`.
`ref` `expr^£`	Returns a `true` value if `expr` is a reference. Returns the package name if `expr` has been blessed into a package.
`reset` [ `llll` ]	Resets `??` searches so that they work again. `llll` is a list of single letters. All variables and arrays beginning with one of those letters are reset to their pristine state. Only affects the current package.
`scalar` `expr`	Evaluates `expr` in scalar context.
`wantarray`	Returns `true` if the current context expects an array value.

Information from System Files

`passwd` returns `($name, $passwd, $uid, $gid, $quota, $comment, $gcos, $dir, $shell)`
`getpwent`	Gets next user information.
`getpwnam` `NAME`	by name.
`getpwuid` `UID`	by user ID.
`endpwent`	Ends lookup processing.
`setpwent`	Resets lookup

`group` returns `($name, $passwd, $gid, $members)`.
`getgrgid` `GID`	by group ID
`getgrnam` `NAME`	by name
`getgrent`	Gets next
`setgrent`	Resets lookup
`endgrent`	Ends lookup

`hosts` returns `($`name, `$`aliases, `$`addrtype, `$`length, `@`addrs`)`.
`gethostbyaddr` `ADDR,` `ADDRTYPE`	Gets information by IP address.
`gethostbyname` `NAME`	Gets information by hostname.
`gethostent`	Gets next host information.
`sethostent` `STAYOPEN`	Resets lookup processing.
`endhostent`	Ends lookup processing.

`networks` returns `($`name, `$`aliases, `$`addrtype, `$`net`)`.
`getnetbyaddr` `ADDR,` `TYPE`	Gets information by address and type.
`getnetbyname` `NAME`	Gets information by network name.
`getnetent`	Gets next network information.
`setnetent` `STAYOPEN`	Resets lookup processing.
`endnetent`	Ends lookup processing.

`services` returns `($`name, `$`aliases, `$`port, `$`proto`)`.
`getservbyname` `NAME,` `PROTO`	Gets information by service name.
`getservbyport` `PORT,` `PROTO`	Gets information by service port.
`getservent`	Gets next service information.
`setservent` `STAYOPEN`	Resets lookup processing.
`endservent`	Ends lookup processing.

`protocols` returns `($`name, `$`aliases, `$`proto`)`.
`getprotobyname` `NAME`	Gets information by protocol name.
`getprotobynumber` `number`	Gets information by protocol number.
`getprotoent`	Gets next protocol information.
`setprotoent` `STAYOPEN`	Resets lookup processing.
`endprotoent`	Ends lookup processing.

Special Variables

Include use English; to use variable names (some match those keywords in awk

global and should be localized in subroutines:
`@_`	`@ARG` parameters passed to subroutine
`$!`	`errno` when used in a numeric context error string when used in a string context
`$@`	error message from the last `eval` or `do` `expr` command.
`$.`	current input line number of the last fh that was read.
`$/`	`$INPUT_RECORD_SEPARATOR` aka `$RS` newline by default. May be multicharacter.
`$\`	`$OUTPUT_RECORD_SEPARATOR for print`
`$,`	`O`utput `F`ield `S`eparator ""
`$"`	`$LIST_SEPERATOR` joins elements of arrays when interpolated in strings. Default space example: `@a[0]='aa'; @a[1]='bb'; $"='+'; print "@a"; aa+bb`
`$;`	`$SUBSCRIPT_SEPARATOR $SUBSEP` for multidimensional array emulation. Default \034, x'1C' ASCII FieldSeperator
`$?`	status returned by the last `…` command, pipe `close` or `system` operator.

`$:`	set of characters after which a string may be broken to fill continuation fields (starting with `^`) in a format.
`@F`	fields of line read in autosplit mode `-a`
`$0`	`$PROGRAM_NAME` being executed. May be assigned to for display in `ps`
`$1,…`	(matches) in `=~ m/` …
`%ENV`	hash of ENVIRONMENT variables, setting on is seen by `fork`ed children
`$$`	`$PROCESS_ID $PID`of the currently executing program. Altered (in child process) by `fork`.
`$<`	`$REAL_USER_ID $UID`
`$>`	`$EFFECTIVE_USER_ID $EUID`
`$(`	`$REAL_GROUP_ID $GID`
`$)`	`$EFFECTIVE_GROUP_ID $EGID`
`$^A`	accumulator for `formline` and `write` operations.
`$^F`	highest system file descriptor, ordinarily 2.
`$^I`	In-place edit extension as passed to Perl using `-i`.
`$^L`	Formfeed character used in formats.
`$^T`	time (as delivered by `time`) when the program started. used by file test operators `-M`, `-A` and `-C`. ( hard to type in if `^T` is the `stty int` key )
`$]`	perl version number, e.g., `5.001`.
`$^D`	debug flags as passed to perl using `-D`.
`$^W`	value of the `-w` option as passed to Perl.
`$^X`	name by which the currently executing program was invoked.
`$^P`	Internal debugging flag.
`$[`	index of the first element in an array, and of the first character in a substring. Default is 0. Deprecated.
`$#`	output format for printed numbers. Deprecated.
`$*`	Set to 1 to do multiline matching within strings. Deprecated, see `m` and `s` modifiers Search and Replace.

context dependent and need not be localized:
`$%`	current page number of the currently selected output channel.
`$=`	page length of the current output channel. Default is 60 lines.
`$-`	number of lines remaining on the page.
`$~`	name of the current report format.
`$^`	name of the current top-of-page format.
`$\|`	If set to nonzero, flushs after write or print on currently selected output channel. Default is 0.
`$ARGV`	name of the current file when reading from `<>`.

local to the current block:
`$&`	string matched by the last successful pattern match.
$`	string preceding ""
`$'`	string following ""
`$+`	last bracket matched by the last search pattern.
`$1`…`$9`…	Contain subpatterns from the corresponding sets of parentheses in the last pattern successfully matched.
`$10`… and up are only available if match contained that many subpatterns.

Special Arrays

`@ARGV`	command-line arguments for the script (not including the command name).
`@EXPORT`	Names the methods a package exports by default.
`@EXPORT_OK`	Names the methods a package can export upon explicit request.
`@INC`	directories to search for `do` `filename` and `require`
`@ISA`	base classes of a package.
`@_`	Parameter array for subroutines. Also used by `split` if not in array context.
`%ENV`	current environment.
`%INC`	List of files that have been included with `require` or `do`.
`%OVERLOAD`	used to overload operators in a package.
`%SIG`	Used to set signal handlers

Environment Variables

Perl uses the following environment variables.

`HOME`	default for `chdir`
`LOGDIR`	default for `chdir` without argument and `HOME` is not set.
`PATH`	Used for subprocesses, and the Perl script with `-S`
`PERL5LIB`	colon-separated list of directories to search for library files before looking in the standard library and the current directory.
`PERL5DB`	The command to get the debugger code. Default: `BEGIN { require 'perl5db.pl' }`.
`PERLLIB`	Used instead of `PERL5LIB` if the latter is not defined.

TOC

The Perl Debugger

Invoked with perl -d. DGG's Version

`h`	Prints out help.
`T`	Prints a stack trace.
`s`	Single steps.
`n`	Single steps around subroutine call.
`RETURN key`	Repeats last `s` or `n`.
`r`	current subroutine.
`c` [ `LINE` ]	Continues (until `LINE`, or another breakpoint, or exit).
`p` `expr`	outputs `expr`.
`l` [ `RANGE` ]	Lists a range of lines. `RANGE` may be a number, start-end, start+amount, or a subroutine name. If `RANGE` is omitted, lists next window.
`w`	Lists window around current line.
`-`	Lists previous window.
`f` `file`	Switches to `file` and starts listing it.
`l` `sub`	the named subroutine.
`S`	names of all subroutines.
`/pattern/`	Searches forward for `pattern`.
`?pattern?`	Searches backward
`b` [ `LINE` [ `CONDITION` ] ]	Sets breakpoint at `LINE`; default is the current line.
`b` `sub` [ `CONDITION` ]	Sets breakpoint at the subroutine.
`d` [ `LINE` ]	Deletes breakpoint at the given line.
`D`	Deletes all breakpoints.
`L`	Lists lines that have breakpoints or actions.
`a` `LINE COMMAND`	Sets an action for line.
`A`	Deletes all line actions.
`<` `COMMAND`	Sets an action to be executed before every debugger prompt.
`>` `COMMAND`	Sets an action to be executed before every `s`, `c` or `n` command.
`V` [ `PACKAGE` [ `VARS` ] ]	Lists all variables in a package. Default package is `main`.
`X` [ `VARS` ]	Like `V`, but assumes current package.
`!` [ [`-`]`number` ]	Re-executes a command. Default is the previous command.
`H` [ -`number` ]	Displays the last `-number` commands of more than one letter.
`t`	Toggles trace mode.
`=` [ `ALIAS VALUE` ]	Sets alias, or lists current aliases.
`q`	Quits. You may also use your `EOF key` character.
`COMMAND`	Executes `COMMAND` as a Perl statement.

Command-Line Options

`-w`	prints warnings about possible spelling errors and other error-prone constructs in the script.
`-d`	runs the script under the debugger. Use `-de 0` to start the debugger without a script
`-D` `number`	sets Debugging flags.
`-F` `REGEXP`	specifies a regular expression to split on
`-p`	assumes an input loop around script. Lines are printed.
`-n`	assumes an input loop around script. Lines are not printed.
`-a`	autosplit mode when used with `-n` or `-p`. Splits to `@F`.
`-c`	checks syntax but does not execute.
`-e` `COMMANDLINE`	enter a single line of script. Multiple `-e` commands may be given to build up a multiline script. if `-a` is in effect.
`-iEXT`	files processed by the `< >` construct are to be edited in place.
`-s`	interprets `-xxx` on the command line as a switch and sets the corresponding variable `$xxx` in the script.
`-S`	Search for the script using the `PATH` environment variable
`-T`	Taint checking.
`-u`	dumps core after compiling the script. To be used with `>undump`.
`-U`	allows perl to perform Unsafe operations.
`-v`	prints the version and patchlevel of your Perl executable.
`-x` [`DIR`]	extracts Perl program from input stream. If `DIR` is specified, `CD`s to this directory before running the program.
`-0VAL`	(zero) Designates an initial value for the Record Separator `$/`. See also `-l`
`-l` [`OCTNUM`]	enables automatic line-end processing, e.g., `-l013` ( ␍ ).
`-P`	runs the C Preprocessor on the script before compilation by Perl.
`-IDIR`	with `-P`, tells the C preprocessor where to look for Include files. The directory is prepended to `@INC`.

Last updated 22 March 2001
[Links updated 7 September 2003]

Rex Swain's HTMLified

Perl 5 Reference Guide

Index

Document Conventions

Quoting:

Escape sequences:

Literals

Variables

Array

Array reference

Hash

reference:

Operators

Statements

Subroutines, Packages and Modules

Object-Oriented Programming

Arithmetic Functions

Conversion Functions

Structure Conversion

String Functions

Array and List Functions

Regular Expressions

Search (Match) and Replace

File Test Operators

File Operations

Input / Output

Formats

Directory Reading Routines

System Interaction

Networking

System V IPC

Miscellaneous

Information from System Files

Special Variables

Special Arrays

Environment Variables

The Perl Debugger

Command-Line Options

See also perldoc.perl.org