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In Unix-like operating systems, unlink is a system call and a command line utility to delete files. The program directly interfaces the system call, which removes the file name and (but not on GNU systems) directories like rm and rmdir . [ 1 ]
Perl autovivification can be contrasted against languages such as Python, PHP, Ruby, and many of the C style languages, where dereferencing null or undefined values is not generally permitted. [ a ] It can be compared to the HTML standard's "named access on the window object" [ 2 ] which results in corresponding globally scoped variables being ...
In functional and list-based languages a string is represented as a list (of character codes), therefore all list-manipulation procedures could be considered string functions. However such languages may implement a subset of explicit string-specific functions as well.
Perl. Block comments in Perl are considered part of the documentation, and are given the name Plain Old Documentation (POD). Technically, Perl does not have a convention for including block comments in source code, but POD is routinely used as a workaround. PHP. PHP supports standard C/C++ style comments, but supports Perl style as well. Python
COBOL uses the STRING statement to concatenate string variables. MATLAB and Octave use the syntax "[x y]" to concatenate x and y. Visual Basic and Visual Basic .NET can also use the "+" sign but at the risk of ambiguity if a string representing a number and a number are together. Microsoft Excel allows both "&" and the function "=CONCATENATE(X,Y)".
Perl 5 has built-in, language-level support for associative arrays. Modern Perl refers to associative arrays as hashes; the term associative array is found in older documentation but is considered somewhat archaic. Perl 5 hashes are flat: keys are strings and values are scalars.
The POSIX directory listing application, ls, denotes symbolic links with an arrow after the name, pointing to the name of the target file (see following example), when the long directory list is requested (-l option). When a directory listing of a symbolic link that points to a directory is requested, only the link itself will be displayed.
An n-component link L ⊂ S 3 is an unlink if and only if there exists n disjointly embedded discs D i ⊂ S 3 such that L = ∪ i ∂D i. A link with one component is an unlink if and only if it is the unknot. The link group of an n-component unlink is the free group on n generators, and is used in classifying Brunnian links.