Introduction to Perl for Unix System Administrators

(Perl without excessive complexity)

by Dr Nikolai Bezroukov

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3.4. Summary and Reference Tables

You can create and initialize arrays in hashes

my @array = (1,3,5,12,37,42); my %hash = ( alpha => 4, beta => 6 );

Scalars are often used for representing and manipulating strings. Perl provides five classic PL/1-style operations on strings (length, concatenation (denoted as . -dot), substr, index and tr -- translate) and a lot of minor, Unix inpired primitives like chop, chomp, uc, lc.

Perl preserves the possibility of using substr on the left side of assignment statement -- the possibility pioneered in PL/1. A very useful string function is split.

Summary of String Functions

Function	Description
`chomp(scalar) chomp(array)`	Intelligent chop. By default removes a newline. Can remove any tail that is specified in a special variable `$/`. Removal is performed only if tail matched $/. Can operate on all elements of an array.
`chop(scalar) chop(array)`	Removes and return the last character from a string. Can operate on arrays. In this case will remove the last character from every element in an array.
`chr(scalar)`	Scalar should a number between 0 and 255. Returns the character that in ASCII code has internal representation (converted to decimal) equal to the `NUMBER`. For example, `chr(65)` returns the letter `A`.
`crypt(scalar1, scalar2)`	Encrypts `STRING1`.
`index(string, substring, start_position)`	Search for a substring in string. Returns the position of the first occurrence of the substring in string at or after `start_position`. If you don't specify start_position, it assumed to be 0 (the beginning of the string). See also rindex
`join(string, array_to_join)`	Opposite to the split function. Concatenate all element of the array and returns the resulting string. The first argument specifies delimiter to be used in the concatenation. For example,`join('.', ('131', '10', '10'))` will return `"131.10.10"`.
`lc(scalar)`	Opposite to uc. Returns a string with every letter of scalar in lowercase. For example, `lc("YAHOO")` returns `"yahoo"`.
`lcfirst(scalar)`	Returns a string with the first letter of scalar in lowercase. For example, `lcfirst("Yahoo")` returns `"yahoo"`.
`length(scalar)`	A classic string operation function. Returns the length of the scalar. Not applicable to arrays and hashes.
`rindex(scalar, substring, start_position)`	Similar to index but return the position of the last occurrence of the substring in string at or after `start_position`. If you don't specify start_position, it assumed to be 0 (the beginning of the string).
`split(regex, string, limit)`	A very important function. Breaks up a string based on some delimiter (can be a regex). In an array context, it returns a list of substrings that match regex. In a scalar context, returns the number of matches found.
`substr(string, offset, length)`	A very important function. Returns a portion of `string` starting from the position specified by the *offset* and length determined by the length parameters. If length is not specified returns tail of the string, starting from the offset position. A negative offset can be used and will count characters from the end of the string.
`tr/fromset/toset/`	The tr function allows character-by-character translation. Has several important options discussed in the text.
`uc(string)`	Opposite to lc. Returns a string with every letter of the string in uppercase. For example, `uc("abba")` returns `"ABBA"`.
`ucfirst(string)`	Opposite to lcfirst. Returns a string with the first letter of the string in uppercase. For example, `ucfirst("nick")` returns `"Nick"`.

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Created: November 7 1998; Last modified: September 05, 2009