当从守护进程运行时Telnet无法正常运行

Question

当我通过交互式shell调用telnet连接到白天服务器时，它工作正常。但是，当从cron或某个bash守护进程运行的shell脚本发出相同的telnet调用时，它不会产生任何输出。我straced两个电话，在这里，他们是：

成功的一个

：

不成功的一个

execve("/usr/bin/telnet", ["telnet", "192.168.0.11", "13"], [/* 24 vars */]) = 0 
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x40005000 
stat("/etc/ld.so.cache", {st_mode=S_IFREG|0644, st_size=3128, ...}) = 0 
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 
mmap2(NULL, 3128, PROT_READ, MAP_SHARED, 3, 0) = 0x40006000 
close(3)        = 0 
stat("/etc/ld.so.preload", 0xbea5d8d4) = -1 ENOENT (No such file or directory) 
open("/lib/libc.so.0", O_RDONLY)  = 3 
fstat(3, {st_mode=S_IFREG|0755, st_size=324423, ...}) = 0 
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x40007000 
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\320\253\0\0004\0\0\0\0"..., 4096) = 4096 
mmap2(NULL, 376832, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4000e000 
mmap2(0x4000e000, 319264, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x4000e000 
mmap2(0x40064000, 4935, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x4e) = 0x40064000 
mmap2(0x40066000, 14712, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x40066000 
close(3)        = 0 
munmap(0x40007000, 4096)    = 0 
munmap(0x40006000, 3128)    = 0 
stat("/lib/ld-uClibc.so.0", {st_mode=S_IFREG|0755, st_size=20486, ...}) = 0 
mprotect(0x40064000, 4096, PROT_READ) = 0 
mprotect(0x4000c000, 4096, PROT_READ) = 0 
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 
ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 
getuid32()        = 0 
ioctl(0, TIOCGWINSZ, {ws_row=55, ws_col=203, ws_xpixel=0, ws_ypixel=0}) = 0 
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 
brk(0)         = 0x91000 
brk(0x92000)       = 0x92000 
socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3 
setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 
connect(3, {sa_family=AF_INET, sin_port=htons(13), sin_addr=inet_addr("192.168.0.11")}, 16) = 0 
setsockopt(3, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0 
rt_sigaction(SIGINT, {0x667c0, [INT], SA_RESTART|0x4000000}, {SIG_DFL, [], 0}, 8) = 0 
poll([{fd=0, events=POLLIN}, {fd=3, events=POLLIN}], 2, -1) = 1 ([{fd=3, revents=POLLIN}]) 
read(3, "Wed Apr 27 11:42:10 2011\r\n"..., 128) = 26 
write(1, "Wed Apr 27 11:42:10 2011\r\n"..., 26) = 26 
poll([{fd=0, events=POLLIN}, {fd=3, events=POLLIN}], 2, -1) = 1 ([{fd=3, revents=POLLIN}]) 
read(3, ""..., 128)      = 0 
write(1, "Connection closed by foreign host"..., 35) = 35 
ioctl(0, SNDCTL_TMR_STOP or TCSETSW, {B38400 opost isig icanon echo ...}) = 0 
exit(1)         = ? 

：

execve("/usr/bin/telnet", ["/usr/bin/telnet", "192.168.0.11", "13"], [/* 22 vars */]) = 0 
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x40005000 
stat("/etc/ld.so.cache", {st_mode=S_IFREG|0644, st_size=3128, ...}) = 0 
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3 
mmap2(NULL, 3128, PROT_READ, MAP_SHARED, 3, 0) = 0x40006000 
close(3)        = 0 
stat("/etc/ld.so.preload", 0xbe90a8f4) = -1 ENOENT (No such file or directory) 
open("/lib/libc.so.0", O_RDONLY)  = 3 
fstat(3, {st_mode=S_IFREG|0755, st_size=324423, ...}) = 0 
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|0x4000000, -1, 0) = 0x40007000 
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\320\253\0\0004\0\0\0\0"..., 4096) = 4096 
mmap2(NULL, 376832, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x4000e000 
mmap2(0x4000e000, 319264, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0x4000e000 
mmap2(0x40064000, 4935, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED, 3, 0x4e) = 0x40064000 
mmap2(0x40066000, 14712, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x40066000 
close(3)        = 0 
munmap(0x40007000, 4096)    = 0 
munmap(0x40006000, 3128)    = 0 
stat("/lib/ld-uClibc.so.0", {st_mode=S_IFREG|0755, st_size=20486, ...}) = 0 
mprotect(0x40064000, 4096, PROT_READ) = 0 
mprotect(0x4000c000, 4096, PROT_READ) = 0 
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbe90a714) = -1 ENOTTY (Inappropriate ioctl for device) 
ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbe90a714) = -1 ENOTTY (Inappropriate ioctl for device) 
getuid32()        = 0 
ioctl(0, TIOCGWINSZ, 0xbe90a9cc)  = -1 ENOTTY (Inappropriate ioctl for device) 
ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, 0xbe90a9b4) = -1 ENOTTY (Inappropriate ioctl for device) 
brk(0)         = 0x91000 
brk(0x92000)       = 0x92000 
socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3 
setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 
connect(3, {sa_family=AF_INET, sin_port=htons(13), sin_addr=inet_addr("192.168.0.11")}, 16) = 0 
setsockopt(3, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0 
rt_sigaction(SIGINT, {0x667c0, [INT], SA_RESTART|0x4000000}, {SIG_DFL, [], 0}, 8) = 0 
poll([{fd=0, events=POLLIN}, {fd=3, events=POLLIN}], 2, -1) = 2 ([{fd=0, revents=POLLIN}, {fd=3, revents=POLLIN}]) 
read(0, ""..., 128)      = 0 
exit(0)         = ? 

任何帮助的欢迎。

Answer 1

呃...管道或分离输入简单地是而不是终端。没有多少环境设置可以解决这个问题。 TRWTF正在使用来自守护进程的telnet

短小故事：使用套接字连接到与您（ab）使用telnet相同的端口。这将大大简化您的设置，并且不需要终端或子进程。

Answer 2

ioctl(0, TIOCGWINSZ, 0xbe90a9cc)  = -1 ENOTTY (Inappropriate ioctl for device) 

我认为这是你的问题。当执行cron时，您没有相同的环境变量，并且您在常规终端中执行此操作。上面的行是两个输出显示的第一个偏差，它看起来像是设置/检查终端窗口大小（WINSZ），大概是telnet会话窗口。也许检查cron脚本中的$TERM的值？