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Message-ID: <CA+dhEd5F3qWFikiABS1QNqY5Dr+YDNVkmcSD4-DuerWsELk4dw@mail.gmail.com> Date: Mon, 10 Feb 2020 12:57:00 +0300 From: Alexander Scherbatiy <alexander.scherbatiy@...l-sw.com> To: musl@...ts.openwall.com, Rich Felker <dalias@...c.org> Subject: Re: fopen with "e" mode to close file descriptor in exec... functions Just a question about lsof options. On Ubuntu "lsof -q" gives: "lsof: illegal option character: q". Shouldn't busybox "lsof -p" give the similar error message? Is there an open request to support "lsof -p" option in busybox? Thanks, Alexandr. On 08.02.2020 19:19, Rich Felker wrote: > On Sat, Feb 08, 2020 at 10:45:10AM +0300, Alexander Scherbatiy wrote: >> Below are steps to reproduce it in docker, logs from docker and strace log. >> >>> docker run --rm -it alpine:3.11.3 ash >>> apk add gcc >>> apk add libc-dev >> Copy the posix_spawn_sample.c code below (note it uses "ash" in 'char >> *argv[] = {"ash", ,,,}' for posix_spawn on Alpine Linux ) >> >>> gcc -o posix_spawn_sample posix_spawn_sample.c >>> ./posix_spawn_sample >> --- output --- >> / # ./posix_spawn_sample >> Child pid: 17 >> PID=17 >> 1 /bin/busybox /dev/pts/0 >> 1 /bin/busybox /dev/pts/0 >> 1 /bin/busybox /dev/pts/0 >> 1 /bin/busybox /dev/tty >> 16 /posix_spawn_sample /dev/pts/0 >> 16 /posix_spawn_sample /dev/pts/0 >> 16 /posix_spawn_sample /dev/pts/0 >> 16 /posix_spawn_sample /test.log >> ---------------- >> >> Note that "test.log" file is listed by "lsof -p PID" command. > It's listed as being owned by pid 16, the parent, not pid 17, the > child. That's expected. At first I didn't understand why lsof -p is > showing these additional pids (parent and init) in addition to the > requested one. But it seems since you're using Docker those are the > *only* pids running, and you just hit the issue that busybox lsof does > not support -p (or any options at all) and always lists all open files > for all processes. > > It would be a lot better to have your test do like I suggested and ls > -l /proc/$$/fd rather than running lsof. Then you will very clearly > that the log file is not open. Or even run an interactive shell as the > child so you can explore /proc yourself from it. > > Rich
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