MSYS shell keeping script file open, preventing modifications

Question

Usually when running a shell script, the shell keeps the script file open throughout the execution. On Unix systems this is not a problem.

However, Windows prevents modifications to a file that is opened in that way. Which means that if a script is running in MSYS, I need to kill the shell before I can modify the script. This is annoying because git pull or svn up will fail.

I am looking for a solution to that problem, for instance through specific options I could put in the #!/bin/sh line, or some kind of shell one-liner that would maybe cause the script to copy itself in a safe place and execute the copy instead.

Answer 1

You could let the script re-exec itself. Split it like this:

#!/bin/sh
if test -z "$MYSCRIPT_REEXEC"; then
    : stuff you do before git pull
    exec env MYSCRIPT_REEXEC=1 sh -c "git pull; . '$0'"
fi
: stuff you do after git pull

This is a simple case, $0 may not contain apostrophs, and the arguments and any variables set in the first half are inaccessible. It’s hard to give a better generic example – maybe, if I could see the original script?

If this still does not work, try this one:

#!/bin/sh
if test -z "$MYSCRIPT_REEXEC"; then
    : stuff you do before git pull
    env MYSCRIPT_REEXEC=1 sh -c "sleep 1; git pull; . '$0'" &
    exit 0
fi
: stuff you do after git pull

In this case, though, return codes will also be all wrong, as will anything waiting for the script.