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. ---------- posix_spawn_sample.c ---------- #include #include #include #include #include #include extern char **environ; int main() { FILE* file = fopen("test.log", "ae"); fprintf(file, "test line\n"); pid_t pid; // use "ash" for Alpine Linux and "bash" for Ubuntu char *argv[] = {"ash", "-c", "echo PID=$$ && lsof -p $$", NULL}; int status = posix_spawn(&pid, "/bin/sh", NULL, NULL, argv, environ); printf("Child pid: %i\n", pid); waitpid(pid, &status, 0); fclose(file); return 0; } -------------------------- The full output step by step: -------------------------------------- > docker run --rm -it alpine:3.11.3 ash / # apk add gcc fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/main/x86_64/APKINDEX.tar.gz fetch http://dl-cdn.alpinelinux.org/alpine/v3.11/community/x86_64/APKINDEX.tar.gz (1/10) Installing libgcc (9.2.0-r3) (2/10) Installing libstdc++ (9.2.0-r3) (3/10) Installing binutils (2.33.1-r0) (4/10) Installing gmp (6.1.2-r1) (5/10) Installing isl (0.18-r0) (6/10) Installing libgomp (9.2.0-r3) (7/10) Installing libatomic (9.2.0-r3) (8/10) Installing mpfr4 (4.0.2-r1) (9/10) Installing mpc1 (1.1.0-r1) (10/10) Installing gcc (9.2.0-r3) Executing busybox-1.31.1-r9.trigger OK: 101 MiB in 24 packages / # apk add libc-dev (1/2) Installing musl-dev (1.1.24-r0) (2/2) Installing libc-dev (0.7.2-r0) OK: 111 MiB in 26 packages / # gcc -o posix_spawn_sample posix_spawn_sample.c / # ./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 -------------------------------------- strace log -------------------------------------- / # strace -f ./posix_spawn_sample execve("./posix_spawn_sample", ["./posix_spawn_sample"], 0x7ffd951eb318 /* 6 vars */) = 0 arch_prctl(ARCH_SET_FS, 0x7f0fa33d6d48) = 0 set_tid_address(0x7f0fa33d731c) = 31 mprotect(0x7f0fa33d3000, 4096, PROT_READ) = 0 mprotect(0x55e26cf7b000, 4096, PROT_READ) = 0 open("test.log", O_WRONLY|O_CREAT|O_APPEND|O_CLOEXEC, 0666) = 3 fcntl(3, F_SETFD, FD_CLOEXEC) = 0 fcntl(3, F_SETFD, FD_CLOEXEC) = 0 fcntl(3, F_GETFL) = 0x8401 (flags O_WRONLY|O_APPEND|O_LARGEFILE) ioctl(3, TIOCGWINSZ, 0x7ffd87e838a8) = -1 ENOTTY (Not a tty) pipe2([4, 5], O_CLOEXEC) = 0 rt_sigprocmask(SIG_BLOCK, ~[], [], 8) = 0 clone(child_stack=0x7ffd87e838b8, flags=CLONE_VM|CLONE_VFORK|SIGCHLDstrace: Process 32 attached [pid 32] close(4) = 0 [pid 32] fcntl(5, F_SETFD, FD_CLOEXEC) = 0 [pid 32] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 [pid 32] execve("/bin/sh", ["ash", "-c", "echo PID=$$ && lsof -p $$"], 0x7ffd87e83998 /* 6 vars */ [pid 31] <... clone resumed>) = 32 [pid 32] <... execve resumed>) = 0 [pid 31] close(5 [pid 32] arch_prctl(ARCH_SET_FS, 0x7f1a19d9ed48 [pid 31] <... close resumed>) = 0 [pid 31] read(4, [pid 32] <... arch_prctl resumed>) = 0 [pid 31] <... read resumed>"", 4) = 0 [pid 32] set_tid_address(0x7f1a19d9f31c [pid 31] close(4 [pid 32] <... set_tid_address resumed>) = 32 [pid 31] <... close resumed>) = 0 [pid 32] mprotect(0x7f1a19d9b000, 4096, PROT_READ [pid 31] rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 [pid 32] <... mprotect resumed>) = 0 [pid 31] ioctl(1, TIOCGWINSZ, {ws_row=40, ws_col=155, ws_xpixel=0, ws_ypixel=0}) = 0 [pid 32] mprotect(0x556eae13a000, 16384, PROT_READ [pid 31] writev(1, [{iov_base="Child pid: 32", iov_len=13}, {iov_base="\n", iov_len=1}], 2 [pid 32] <... mprotect resumed>) = 0Child pid: 32 [pid 31] <... writev resumed>) = 14 [pid 31] wait4(32, [pid 32] getuid() = 0 [pid 32] getpid() = 32 [pid 32] rt_sigprocmask(SIG_UNBLOCK, [RT_1 RT_2], NULL, 8) = 0 [pid 32] rt_sigaction(SIGCHLD, {sa_handler=0x556eae0b9dfc, sa_mask=~[RTMIN RT_1 RT_2], sa_flags=SA_RESTORER, sa_restorer=0x7f1a19d500d4}, NULL, 8) = 0 [pid 32] rt_sigaction(SIGHUP, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=SA_RESTORER|SA_RESTART, sa_restorer=0x7f1a19d500d4}, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0 [pid 32] getppid() = 31 [pid 32] stat("/", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 [pid 32] stat(".", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0 [pid 32] rt_sigaction(SIGINT, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0 [pid 32] rt_sigaction(SIGINT, {sa_handler=0x556eae0b9dfc, sa_mask=~[RTMIN RT_1 RT_2], sa_flags=SA_RESTORER, sa_restorer=0x7f1a19d500d4}, NULL, 8) = 0 [pid 32] rt_sigaction(SIGQUIT, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0 [pid 32] rt_sigaction(SIGQUIT, {sa_handler=SIG_IGN, sa_mask=~[RTMIN RT_1 RT_2], sa_flags=SA_RESTORER, sa_restorer=0x7f1a19d500d4}, NULL, 8) = 0 [pid 32] rt_sigaction(SIGTERM, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0 [pid 32] wait4(-1, 0x7fff4e3ea22c, WNOHANG, NULL) = -1 ECHILD (No child process) [pid 32] write(1, "PID=32\n", 7PID=32 ) = 7 [pid 32] stat("/usr/local/sbin/lsof", 0x7fff4e3ea170) = -1 ENOENT (No such file or directory) [pid 32] stat("/usr/local/bin/lsof", 0x7fff4e3ea170) = -1 ENOENT (No such file or directory) [pid 32] stat("/usr/sbin/lsof", 0x7fff4e3ea170) = -1 ENOENT (No such file or directory) [pid 32] stat("/usr/bin/lsof", {st_mode=S_IFREG|0755, st_size=841288, ...}) = 0 [pid 32] brk(NULL) = 0x556eaf7c5000 [pid 32] brk(0x556eaf7c6000) = 0x556eaf7c6000 [pid 32] execve("/usr/bin/lsof", ["lsof", "-p", "32"], 0x556eae13ed80 /* 6 vars */) = 0 [pid 32] arch_prctl(ARCH_SET_FS, 0x7fe42bc41d48) = 0 [pid 32] set_tid_address(0x7fe42bc4231c) = 32 [pid 32] mprotect(0x7fe42bc3e000, 4096, PROT_READ) = 0 [pid 32] mprotect(0x55d56c79b000, 16384, PROT_READ) = 0 [pid 32] getuid() = 0 [pid 32] open("/proc", O_RDONLY|O_CLOEXEC|O_DIRECTORY) = 3 [pid 32] fcntl(3, F_SETFD, FD_CLOEXEC) = 0 [pid 32] getdents64(3, /* 67 entries */, 2048) = 1984 [pid 32] readlink("/proc/1/exe", "/bin/busybox", 80) = 12 [pid 32] getpid() = 32 [pid 32] open("/proc/1/fd/", O_RDONLY|O_CLOEXEC|O_DIRECTORY) = 4 [pid 32] fcntl(4, F_SETFD, FD_CLOEXEC) = 0 [pid 32] brk(NULL) = 0x55d56dac0000 [pid 32] brk(0x55d56dac1000) = 0x55d56dac1000 [pid 32] getdents64(4, /* 6 entries */, 2048) = 144 [pid 32] readlink("/proc/1/fd/0", "/dev/pts/0", 80) = 10 [pid 32] ioctl(1, TIOCGWINSZ, {ws_row=40, ws_col=155, ws_xpixel=0, ws_ypixel=0}) = 0 [pid 32] writev(1, [{iov_base="1\t/bin/busybox\t/dev/pts/0", iov_len=25}, {iov_base="\n", iov_len=1}], 21 /bin/busybox /dev/pts/0 ) = 26 [pid 32] readlink("/proc/1/fd/1", "/dev/pts/0", 80) = 10 [pid 32] writev(1, [{iov_base="1\t/bin/busybox\t/dev/pts/0", iov_len=25}, {iov_base="\n", iov_len=1}], 21 /bin/busybox /dev/pts/0 ) = 26 [pid 32] readlink("/proc/1/fd/2", "/dev/pts/0", 80) = 10 [pid 32] writev(1, [{iov_base="1\t/bin/busybox\t/dev/pts/0", iov_len=25}, {iov_base="\n", iov_len=1}], 21 /bin/busybox /dev/pts/0 ) = 26 [pid 32] readlink("/proc/1/fd/10", "/dev/tty", 80) = 8 [pid 32] writev(1, [{iov_base="1\t/bin/busybox\t/dev/tty", iov_len=23}, {iov_base="\n", iov_len=1}], 21 /bin/busybox /dev/tty ) = 24 [pid 32] getdents64(4, /* 0 entries */, 2048) = 0 [pid 32] close(4) = 0 [pid 32] readlink("/proc/28/exe", "/usr/bin/strace", 80) = 15 [pid 32] getpid() = 32 [pid 32] open("/proc/28/fd/", O_RDONLY|O_CLOEXEC|O_DIRECTORY) = 4 [pid 32] fcntl(4, F_SETFD, FD_CLOEXEC) = 0 [pid 32] getdents64(4, /* 5 entries */, 2048) = 120 [pid 32] readlink("/proc/28/fd/0", "pipe:[89317]", 80) = 12 [pid 32] writev(1, [{iov_base="28\t/usr/bin/strace\tpipe:[89317]", iov_len=31}, {iov_base="\n", iov_len=1}], 228 /usr/bin/strace pipe:[89317] ) = 32 [pid 32] readlink("/proc/28/fd/1", "pipe:[89318]", 80) = 12 [pid 32] writev(1, [{iov_base="28\t/usr/bin/strace\tpipe:[89318]", iov_len=31}, {iov_base="\n", iov_len=1}], 228 /usr/bin/strace pipe:[89318] ) = 32 [pid 32] readlink("/proc/28/fd/2", "/dev/pts/0", 80) = 10 [pid 32] writev(1, [{iov_base="28\t/usr/bin/strace\t/dev/pts/0", iov_len=29}, {iov_base="\n", iov_len=1}], 228 /usr/bin/strace /dev/pts/0 ) = 30 [pid 32] getdents64(4, /* 0 entries */, 2048) = 0 [pid 32] close(4) = 0 [pid 32] readlink("/proc/31/exe", "/posix_spawn_sample", 80) = 19 [pid 32] getpid() = 32 [pid 32] open("/proc/31/fd/", O_RDONLY|O_CLOEXEC|O_DIRECTORY) = 4 [pid 32] fcntl(4, F_SETFD, FD_CLOEXEC) = 0 [pid 32] getdents64(4, /* 6 entries */, 2048) = 144 [pid 32] readlink("/proc/31/fd/0", "/dev/pts/0", 80) = 10 [pid 32] writev(1, [{iov_base="31\t/posix_spawn_sample\t/dev/pts/"..., iov_len=33}, {iov_base="\n", iov_len=1}], 231 /posix_spawn_sample /dev/pts/0 ) = 34 [pid 32] readlink("/proc/31/fd/1", "/dev/pts/0", 80) = 10 [pid 32] writev(1, [{iov_base="31\t/posix_spawn_sample\t/dev/pts/"..., iov_len=33}, {iov_base="\n", iov_len=1}], 231 /posix_spawn_sample /dev/pts/0 ) = 34 [pid 32] readlink("/proc/31/fd/2", "/dev/pts/0", 80) = 10 [pid 32] writev(1, [{iov_base="31\t/posix_spawn_sample\t/dev/pts/"..., iov_len=33}, {iov_base="\n", iov_len=1}], 231 /posix_spawn_sample /dev/pts/0 ) = 34 [pid 32] readlink("/proc/31/fd/3", "/test.log", 80) = 9 [pid 32] writev(1, [{iov_base="31\t/posix_spawn_sample\t/test.log", iov_len=32}, {iov_base="\n", iov_len=1}], 231 /posix_spawn_sample /test.log ) = 33 [pid 32] getdents64(4, /* 0 entries */, 2048) = 0 [pid 32] close(4) = 0 [pid 32] readlink("/proc/32/exe", "/bin/busybox", 80) = 12 [pid 32] getpid() = 32 [pid 32] getdents64(3, /* 0 entries */, 2048) = 0 [pid 32] close(3) = 0 [pid 32] exit_group(0) = ? [pid 32] +++ exited with 0 +++ <... wait4 resumed>[{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 32 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=32, si_uid=0, si_status=0, si_utime=0, si_stime=0} --- writev(3, [{iov_base="test line\n", iov_len=10}, {iov_base=NULL, iov_len=0}], 2) = 10 close(3) = 0 exit_group(0) = ? +++ exited with 0 +++ -------------------------------------- Thanks, Alexander. On Sat, Feb 8, 2020 at 12:03 AM Rich Felker wrote: > On Fri, Feb 07, 2020 at 09:22:01PM +0300, Alexander Scherbatiy wrote: > > Hello, > > > > Below is a simple program without any errors handling that uses > > fopen with "ae" mode to open a "test.log" file with append access > > and call posix_spawn to create a child process and list all open files > for > > the child process. > > > > The program output shows that the child process has "test.log" file as > open. > > I used docker with Alpine Linux 3.11.3 (musl libc x86_64 1.1.24). > > Is it an expected behaviour for Alpine Linux? > > > > The same program on my Ubuntu 19.10 (with "ash" changed to "bash") shows > > that > > the child process doesn't have "test.log" file as open. > > > > Thanks, > > Alexander. > > > > ---------- posix_spawn_sample.c ---------- > > #include > > #include > > #include > > > > #include > > #include > > #include > > > > extern char **environ; > > > > int main() > > { > > FILE* file = fopen("test.log", "ae"); > > fprintf(file, "test line\n"); > > > > pid_t pid; > > char *argv[] = {"bash", "-c", "echo PID=$$ && lsof -p $$", NULL}; > > int status = posix_spawn(&pid, "/bin/sh", NULL, NULL, argv, environ); > > printf("Child pid: %i\n", pid); > > waitpid(pid, &status, 0); > > > > fclose(file); > > return 0; > > } > > -------------------------- > > I can't reproduce this. I had to change /bin/sh to /bin/bash to be > able to run the test at all, and the lsof I have (busybox) doesn't > support -p, but I can't see any indication that the child has the log > file open. I also tried changing it to run "ls -l /proc/$$/fd" in the > child, and a fd 3 shows up there but prints an error because fd 3 is > the directory fd for listing /proc/$$/fd and it's closed before trying > to stat it -- apparently ash execs ls rather than running it as a > child. Indeed adding "; echo" makes that go away. > > If you're still having the problem, could you attach a log of running > your test under "strace -f"? > > Rich >