here文档，又称作heredoc、hereis、here-字串或here-脚本，是一种在命令行shell（如sh、csh、ksh、bash、PowerShell和zsh）和进程语言（像Perl、PHP、Python和Ruby）里定义一个字串的方法。它可以保存文本里面的换行或是缩进等空白字符。一些语言允许在字串里执行变量替换和命令替换。

here文档最通用的语法是<<紧跟一个标识符，从下一行开始是想要引用的文本，然后再在单独的一行用相同的标识符关闭。在Unix shell里，here文档通常用于给命令提供输入内容。

In computing, a here document (here-document, heredoc, hereis, here-string or here-script) is a file literal or input stream literal: it is a section of a source code file that is treated as if it were a separate file. The term is also used for a form of multiline string literals that use similar syntax, preserving line breaks and other whitespace (including indentation) in the text.