On 2008-05-10, Dennis Lee Bieber <[EMAIL PROTECTED]> wrote: >> These are the minute details that bedevil the poor noob. I've >> read dozens of tutorials on different prog langs and have >> never read a single thing on white space or blank lines >> preceding a shebang. Till now. I always get > > Well... The "shebang" line is OS and shell specific
The "#!" is sort of a holdover from the "magic number" used back in the day on Unix systems. Traditionally, the type of an executable file on Unix systems was determined by a "magic number" that was read from the first two bytes of a file: http://en.wikipedia.org/wiki/Magic_number_(programming) Back then there was a text file somewhere that listed the various 16-bit values and what they meant. The "file" program used that list to guess what a file was. It's gotten considerably more complex since then, and the "magic" file has syntax to specify fairly large/complex patterns that are used to determine file types. If you're curious, there's probably a "magic" file somewhere on your system. On Gentoo it's at /usr/share/misc/file/magic, On a Linux system (and I presume on other Unixes), the kernel itself (if built with the proper options) knows know how start a "script" file that starts with the characters "#!". When the kernel is told to execute a file whose first two bytes are "#!" (0x32,0x21), it knows to read the newline terminated path of an executable starting at the byte following the "!" (the third byte in the file). The kernel then executes that file, appending the name of the original "script" file to the argv list. -- Grant Edwards grante Yow! My mind is making at ashtrays in Dayton ... visi.com -- http://mail.python.org/mailman/listinfo/python-list
