Hi, David Wright wrote: > As I posted, I get the same behaviour whichever shebang I have, > any of bash|dash|sh.
That's probably because there is bash-ism in the script, except the variable READLINE_LINE which the boss bash is supposed to have set. > If the script has no shebang, then (I assume) the system will run a > shell to execute it. As under correction above, it appears to start up > this new shell with the same command line as the one it's running in. https://manpages.debian.org/stretch/bash/bash.1.en.html says after having explained how the file is looked up: If the search is successful, or if the command name contains one or more slashes, the shell executes the named program in a separate execution environment. Argument 0 is set to the name given, and the remaining arguments to the command are set to the arguments given, if any. So it may be that the Linux kernel decides what to do. The man page goes on with: If this execution fails because the file is not in executable format, and the file is not a directory, it is assumed to be a shell script, a file containing shell commands. A subshell is spawned to execute it. This subshell reinitializes itself, so that the effect is as if a new shell had been invoked to handle the script, with the exception that the locations of commands remembered by the parent (see hash below under SHELL BUILTIN COMMANDS) are retained by the child. I'd expect that a script without "#!" falls in this category. It seems that here we have the difference between Jessie and Stretch. The man page then explains what happens if "#!" is seen: If the program is a file beginning with #!, the remainder of the first line specifies an interpreter for the program. The shell executes the specified interpreter on operating systems that do not handle this executable format themselves. So again, it may be that the kernel decides to execute the interpreter program with the script, or it can tell the shell to handle this on its own. Whatever happens, it works on Stretch. My main suspect would be the statement in the middle quote about scripts without "#!": "This subshell reinitializes itself" Obviously this differs from the initialization of a freshly started new shell, or from the cleanup in the momma shell before the fork and start of an external program. Have a nice day :) Thomas
