flock before execve?
I’m seeing some funky “new” (to me) behavior that I’m having trouble tracking down. Maybe y’all have seen it before. Using kernel 2.6.18-6-686 (debian etch), I can have a shell script open in vi, and suspend vi to run it. But on 2.6.26-1-686 (debian lenny) I get this error:
host:~/dir# ./shellscript -foo
-bash: ./shellscript: /bin/bash: bad interpreter: Text file busy
If I exit out of vi I can run the script just fine. I can also run the script with “sh shellscript”. strace reveals that the failure is happening super early on:
host:~/dir# strace ./shellscript -foo
execve("./shellscript", ["./shellscript", "-foo"], [/* 19 vars */]) = -1 ETXTBSY (Text file busy)
It looks like the kernel must be checking for exclusive advisory locks before proceeding. I have checked around Google and I see others have had the same trouble, and they’re always told to make sure the file isn’t open by some other process. But I can’t find where new behavior was introduced. Best I can gather, it’s just accepted as the norm now. Seems awfully weird to me.
UPDATE: As noted in the comments, the kernel isn’t doing flock before execve. It’s just preventing you from running commands if the file is open for writing. It’s old behavior. I only saw it now because old nvi didn’t keep the write file handle open (or at least, not in the same way) and new nvi does.