shebang sometimes also called hashbang is the common name for the sequence of characters used at the start of a shell script, taking the form of a hash followed by an exclamation mark:
The name derives from the "sh" sound at the end of "hash", plus "bang" which is a short name for the exclamation mark.
When used in a shell script the hash symbol typically denotes the beginning of a comment. However in the particular case of the shebang sequence occurring as the first two characters of a file, the running shell will treat the rest of first line as a path to the interpreter required to execute the script. For instance:
#!/usr/bin/perl #!/usr/local/bin/bash #!/bin/sh #!/bin/awk -f
Env(command) -- see the special trick section