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Interpreter directive
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<p>An interpreter directive is a <a href="/facts/Computer_language/n3L56qdP">computer language</a> construct, that on some systems is better described as an aspect of the system's executable file format, that is used to control which <a href="/facts/Interpreter_(computing)/JB85fbyb">interpreter</a> parses and interprets the instructions in a <a href="/facts/Computer_program/e38jH9N9">computer program</a>. </p><p>In <a href="/facts/Unix/0pNL2seI">Unix</a>, <a href="/facts/Linux/9FvCKSTq">Linux</a> and other <a href="/facts/Unix-like/YAKrAxzd">Unix-like</a> <a href="/facts/Operating_system/8XTuvMh2">operating systems</a>, the first two bytes in a file can be the characters "#!", which constitute a <a href="/facts/Magic_number_(programming)/Xg7mVI7V">magic number</a> (<a href="/facts/Hexadecimal/02ohQW22">hexadecimal</a> 23 and 21, the ASCII values of "#" and "!") often referred to as <a href="/facts/Shebang_(Unix)/brtu1F1o">shebang</a>, prefix the first line in a <a href="/facts/Script_(Unix)/ovxq1fUF">script</a>, with the remainder of the line being a command usually limited to a max of 14 (when introduced) up to usually about 80 characters in 2016. If the <a href="/facts/File_system_permissions/DHq5SwI4">file system permissions</a> on the script (a file) include an <a href="/facts/Execution_(computing)/1fyfGMFm">execute</a> permission bit for the user invoking it by its filename (often found through the command search path), it is used to tell the operating system what interpreter (usually a program that implements a <a href="/facts/Scripting_language/8pF4ajBL">scripting language</a>) to use to execute the <a href="/facts/Shell_script/NE7YvsBD">script</a>'s contents, which may be <a href="/facts/Batch_processing/hKY2rX3N">batch commands</a> or might be intended for interactive use. An example would be <i>#!/bin/bash</i>, meaning run this script with the <a href="/facts/Bash_(Unix_shell)/RrYLtEJT">bash shell</a> found in the /bin <a href="/facts/Unix_filesystem/qWU9Tlnh">directory</a>. </p><p>Other systems or files may use some other <i><a href="/facts/Magic_number_(programming)/Xg7mVI7V">magic number</a></i> as the interpreter directives. </p>