terminal: ways of executing binaries and scripts

David the H. · 07-31-2012, 02:19 PM

Direct execution is when you use the script name itself as the command name, including the relative and absolute path versions in the above discussion.

source and launching a specific shell name as the main command mean that the script becomes an argument to that command, and the file is read, not executed.

carwe · 07-31-2012, 05:01 PM

Quote:

Originally Posted by David the H.

Direct execution is when you use the script name itself as the command name, including the relative and absolute path versions in the above discussion.

source and launching a specific shell name as the main command mean that the script becomes an argument to that command, and the file is read, not executed.

OK, so that would mean that the she-bang is respected when executing a script (using the script name as the command), but not when calling through 'source' or giving the script as an argument to 'sh', 'bash', etc.

theNbomr · 07-31-2012, 05:54 PM

The she-bang notation is used by the kernel when it launches an executable. If it sees the she-bang, it loads the specified interpreter (can be anything at all, not just a shell), and passes the name of the script as its first commandline argument. The interpeter then opens the file, and interprets the contents.
'Sourcing' is done by an already-running shell itself, and is a behavior of those shells (possibly all major shells).

[EDIT] #! - the Unix truth as far as I know it. explains this in some detail.