九月 | 2016 | 夜行船

我有一段脚本自己的mac机器默认用zsh，运行时一直很正常，今天给别的同事用，在bash下有些异常，追查了一下这个问题，把问题简化后如下：

#!/bin/bash
zsh -ic "which mvn"
zsh -ic "which mvn"

上面的脚本执行没有问题，但将里面的zsh换位bash，就会出现问题：

#!/bin/bash
bash -ic "which mvn"
bash -ic "which mvn"

在mac上执行，第一次bash -ic "which mvn"是成功的，但第二次执行时就会挂住：

 ➜  ./b.sh
/usr/local/bin/mvn
[1]  + 24649 suspended (tty input)  ./b.sh

/tmp/dd   [23:43:21]
[jobs:1] ➜

后来想到which在zsh里是一个内置命令，而在bash下则是一个外部命令，可能有所差异，将zsh执行的命令也声明为外部命令：

#!/bin/bash
zsh -ic "/usr/bin/which mvn"
zsh -ic "/usr/bin/which mvn"

执行时会在第二次阻塞住，即使Ctrl-C也无法停止脚本。

这个问题很奇怪，两次以交互式调用shell执行一段命令（必须是外部命令）的话，第一次会成功，第二次则会suspend住。猜测可能是shell在第一次交互式执行结束后改变了上下文的什么状态，导致第二次再执行的时候挂住。在linux上用strace跟踪了一下脚本，看样子是因为SIGTTIN信号量所致，但其中缘由并不清楚，我把代码和strace的信息贴在这里，希望明白的人解释一下

$ cat b.sh
#!/bin/bash
bash -ic "ls"
bash -ic "ls"

$ strace ./b.sh

[hongjiang@localhost dd]$ strace ./b.sh
execve("./b.sh", ["./b.sh"], [/* 31 vars */]) = 0
brk(0)                                  = 0x1175000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa545ddf000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=32094, ...}) = 0
mmap(NULL, 32094, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fa545dd7000
close(3)                                = 0
open("/lib64/libtinfo.so.5", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0@\316\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=174520, ...}) = 0
mmap(NULL, 2268928, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fa545995000
mprotect(0x7fa5459ba000, 2097152, PROT_NONE) = 0
mmap(0x7fa545bba000, 20480, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x25000) = 0x7fa545bba000
close(3)                                = 0
open("/lib64/libdl.so.2", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320\16\0\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=19512, ...}) = 0
mmap(NULL, 2109744, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fa545791000
mprotect(0x7fa545794000, 2093056, PROT_NONE) = 0
mmap(0x7fa545993000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2000) = 0x7fa545993000
close(3)                                = 0
open("/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\0\34\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2107760, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa545dd6000
mmap(NULL, 3932736, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fa5453d0000
mprotect(0x7fa545586000, 2097152, PROT_NONE) = 0
mmap(0x7fa545786000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1b6000) = 0x7fa545786000
mmap(0x7fa54578c000, 16960, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fa54578c000
close(3)                                = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa545dd4000
arch_prctl(ARCH_SET_FS, 0x7fa545dd4740) = 0
mprotect(0x7fa545786000, 16384, PROT_READ) = 0
mprotect(0x7fa545993000, 4096, PROT_READ) = 0
mprotect(0x7fa545bba000, 16384, PROT_READ) = 0
mprotect(0x6dc000, 4096, PROT_READ)     = 0
mprotect(0x7fa545de0000, 4096, PROT_READ) = 0
munmap(0x7fa545dd7000, 32094)           = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
open("/dev/tty", O_RDWR|O_NONBLOCK)     = 3
close(3)                                = 0
brk(0)                                  = 0x1175000
brk(0x1196000)                          = 0x1196000
brk(0)                                  = 0x1196000
open("/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=106065056, ...}) = 0
mmap(NULL, 106065056, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fa53eea9000
close(3)                                = 0
brk(0)                                  = 0x1196000
getuid()                                = 1000
getgid()                                = 1000
geteuid()                               = 1000
getegid()                               = 1000
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
open("/proc/meminfo", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fa545dde000
read(3, "MemTotal:        1017160 kB\nMemF"..., 1024) = 1024
close(3)                                = 0
munmap(0x7fa545dde000, 4096)            = 0
rt_sigaction(SIGCHLD, {SIG_DFL, [], SA_RESTORER|SA_RESTART, 0x7fa545405650}, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGCHLD, {SIG_DFL, [], SA_RESTORER|SA_RESTART, 0x7fa545405650}, {SIG_DFL, [], SA_RESTORER|SA_RESTART, 0x7fa545405650}, 8) = 0
rt_sigaction(SIGINT, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGINT, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, 8) = 0
rt_sigaction(SIGQUIT, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, {SIG_DFL, [], 0}, 8) = 0
rt_sigaction(SIGQUIT, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, 8) = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
rt_sigaction(SIGQUIT, {SIG_IGN, [], SA_RESTORER, 0x7fa545405650}, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, 8) = 0
uname({sys="Linux", node="localhost.localdomain", ...}) = 0
stat("/tmp/dd", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
stat(".", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
getpid()                                = 2945
open("/usr/lib64/gconv/gconv-modules.cache", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=26254, ...}) = 0
mmap(NULL, 26254, PROT_READ, MAP_SHARED, 3, 0) = 0x7fa545dd8000
close(3)                                = 0
getppid()                               = 2942
getpgrp()                               = 2942
rt_sigaction(SIGCHLD, {0x441090, [], SA_RESTORER|SA_RESTART, 0x7fa545405650}, {SIG_DFL, [], SA_RESTORER|SA_RESTART, 0x7fa545405650}, 8) = 0
getrlimit(RLIMIT_NPROC, {rlim_cur=3909, rlim_max=3909}) = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
open("./b.sh", O_RDONLY)                = 3
ioctl(3, SNDCTL_TMR_TIMEBASE or SNDRV_TIMER_IOCTL_NEXT_DEVICE or TCGETS, 0x7fff54edec40) = -1 ENOTTY (Inappropriate ioctl for device)
lseek(3, 0, SEEK_CUR)                   = 0
read(3, "#!/bin/sh\n\nbash -ic \"ls\"\nbash -i"..., 80) = 39
lseek(3, 0, SEEK_SET)                   = 0
getrlimit(RLIMIT_NOFILE, {rlim_cur=1024, rlim_max=4*1024}) = 0
fcntl(255, F_GETFD)                     = -1 EBADF (Bad file descriptor)
dup2(3, 255)                            = 255
close(3)                                = 0
fcntl(255, F_SETFD, FD_CLOEXEC)         = 0
fcntl(255, F_GETFL)                     = 0x8000 (flags O_RDONLY|O_LARGEFILE)
fstat(255, {st_mode=S_IFREG|0775, st_size=39, ...}) = 0
lseek(255, 0, SEEK_CUR)                 = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
read(255, "#!/bin/sh\n\nbash -ic \"ls\"\nbash -i"..., 39) = 39
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
stat(".", {st_mode=S_IFDIR|0775, st_size=4096, ...}) = 0
stat("/home/hongjiang/.local/bin/bash", 0x7fff54ede900) = -1 ENOENT (No such file or directory)
stat("/home/hongjiang/bin/bash", 0x7fff54ede900) = -1 ENOENT (No such file or directory)
stat("/data/program/scala/bin/bash", 0x7fff54ede900) = -1 ENOENT (No such file or directory)
stat("/usr/lib64/qt-3.3/bin/bash", 0x7fff54ede900) = -1 ENOENT (No such file or directory)
stat("/usr/local/bin/bash", 0x7fff54ede900) = -1 ENOENT (No such file or directory)
stat("/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=960384, ...}) = 0
stat("/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=960384, ...}) = 0
geteuid()                               = 1000
getegid()                               = 1000
getuid()                                = 1000
getgid()                                = 1000
access("/usr/bin/bash", X_OK)           = 0
stat("/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=960384, ...}) = 0
geteuid()                               = 1000
getegid()                               = 1000
getuid()                                = 1000
getgid()                                = 1000
access("/usr/bin/bash", R_OK)           = 0
stat("/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=960384, ...}) = 0
stat("/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=960384, ...}) = 0
geteuid()                               = 1000
getegid()                               = 1000
getuid()                                = 1000
getgid()                                = 1000
access("/usr/bin/bash", X_OK)           = 0
stat("/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=960384, ...}) = 0
geteuid()                               = 1000
getegid()                               = 1000
getuid()                                = 1000
getgid()                                = 1000
access("/usr/bin/bash", R_OK)           = 0
rt_sigprocmask(SIG_BLOCK, [INT CHLD], [], 8) = 0
lseek(255, -14, SEEK_CUR)               = 25
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fa545dd4a10) = 2946
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGINT, {0x43e500, [], SA_RESTORER, 0x7fa545405650}, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, 8) = 0
wait4(-1, b.sh
[{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 2946
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=2946, si_status=0, si_utime=0, si_stime=0} ---
wait4(-1, 0x7fff54ede450, WNOHANG, NULL) = -1 ECHILD (No child processes)
rt_sigreturn()                          = 0
rt_sigaction(SIGINT, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, {0x43e500, [], SA_RESTORER, 0x7fa545405650}, 8) = 0
rt_sigprocmask(SIG_BLOCK, NULL, [], 8)  = 0
read(255, "bash -ic \"ls\"\n", 39)      = 14
stat("/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=960384, ...}) = 0
stat("/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=960384, ...}) = 0
geteuid()                               = 1000
getegid()                               = 1000
getuid()                                = 1000
getgid()                                = 1000
access("/usr/bin/bash", X_OK)           = 0
stat("/usr/bin/bash", {st_mode=S_IFREG|0755, st_size=960384, ...}) = 0
geteuid()                               = 1000
getegid()                               = 1000
getuid()                                = 1000
getgid()                                = 1000
access("/usr/bin/bash", R_OK)           = 0
rt_sigprocmask(SIG_BLOCK, [INT CHLD], [], 8) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fa545dd4a10) = 2967
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGINT, {0x43e500, [], SA_RESTORER, 0x7fa545405650}, {SIG_DFL, [], SA_RESTORER, 0x7fa545405650}, 8) = 0
wait4(-1, 0x7fff54edea00, 0, NULL)      = ? ERESTARTSYS (To be restarted if SA_RESTART is set)
--- SIGTTIN {si_signo=SIGTTIN, si_code=SI_USER, si_pid=2967, si_uid=1000} ---
--- stopped by SIGTTIN ---

我们在招Java/Scala的资深工程师(或技术专家)，你将有机会跟我们共同参与一些挖财基础设施的开发。如果你有Akka的应用经验更好，不过掌握Scala/Akka并不是必要条件，基本的要求是功底扎实，对分布式有一定的了解。至少有三年以上的工作经验，本科或以上学历。工作地点在杭州。

关于挖财的技术你可以通过InfoQ或ArchSummit搜到一些相关的分享，业务开发语言以Java为主Scala为辅。现阶段技术人员有两百多人的规模，这几年早已从初创时期的个人英雄主义转变为中等规模的集团军作战方式。整体上我们算是偏中庸的一个技术团队，也形成了一套适合自己的技术栈，相对务实，没有太多花活。

业务当前发展比较快，对技术的要求也是不断在提升，对该职位感兴趣的请发邮件到: cuodao(at)wacai.com ，每封邮件一定回复。

夜行船

月度归档：2016年09月

SIGTTIN?

招聘资深Java/Scala工程师