Heredoc

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A Heredoc , also called here document (from English , literally here document ), is a language concept in computer science for the specification of a character string literal in command line interpreters such as bash , Windows PowerShell and the Bourne Shell as well as in programming languages such as Perl , PHP , Python and Ruby . According to the designation, Heredocs are used to define sections of text. In contrast to conventional string definitions , contained line breaks, indents and many special characters are preserved in the text. Some languages ​​also allow the interpolation of variables or program code within the character string.

Depending on the programming language heredocs be <<, <<<, <!--, <<-or similar strings initiated, followed by an arbitrary delimiter specifiers (separator); the text to be assigned follows in the following lines. The end of the Heredoc is marked by a line with the previously selected identifier and, if necessary, a terminating semicolon.

Many UNIX shells, including the Bourne shell (sh) and zsh, offer Heredocs as a way of specifying input values ​​for command line commands. The Microsoft PowerShell provides similar functionality, both interactively in the shell itself, as well as a special script syntax script files that are executable in PowerShell.

Exemplary implementation in PHP :

<?php
echo <<<ENDE
Dies ist ein Heredoc
zweite Zeile
ENDE;
?>

See also