Re: On write command
On 31/01/2011 01:52, Larry Hall (Cygwin) wrote:
On 1/29/2011 8:20 AM, Angelo Graziosi wrote:
I would ask if on Cygwin I can use the 'write' command:
write - send a message to another user
$ write USER [ttyname]
I remember I have used it some years ago, but not remember if it was on
GNU/Linux or Cygwin.
I did a research on http://cygwin.com/packages and didn't find it, but
perhaps I did the wrong search..
No, that's the correct place to search. If it's not showing up, none of
the current packages provide 'write'.
It's part of util-linux, but it's configured out of the build on Cygwin,
because it relies on a working utmp file to operate. Which we don't have.
Hmm, I'm in the middle of a gcc testrun right now and can't rebuild my DLL,
but I noticed a few interesting points about the code:
winsup/cygwin/include/utmpx.h
/* Must be kept in sync with struct utmp as defined in sys/utmp.h! */
struct utmpx
{
shortut_type;
pid_tut_pid;
char ut_line[UT_LINESIZE];
char ut_id[UT_IDLEN];
time_t ut_time;
char ut_user[UT_NAMESIZE];
char ut_host[UT_HOSTSIZE];
long ut_addr;
struct timeval ut_tv;
};
winsup/cygwin/include/sys/utmp.h
struct utmp
{
shortut_type;
pid_tut_pid;
char ut_line[UT_LINESIZE];
char ut_id[UT_IDLEN];
time_t ut_time;
char ut_user[UT_NAMESIZE];
char ut_host[UT_HOSTSIZE];
long ut_addr;
};
That could explain why successive calls to getutent() appear to lose frame
across the contents of utmp. Also,
winsup/cygwin/syscalls.cc
/* Note: do not make NO_COPY */
static struct utmp utmp_data_buf[16];
static unsigned utix = 0;
#define nutdbuf (sizeof (utmp_data_buf) / sizeof (utmp_data_buf[0]))
#define utmp_data ({ \
if (utix nutdbuf) \
utix = 0; \
utmp_data_buf + utix++; \
})
I haven't slept all night, but isn't that going to overrun by one? Anyway
with the fix to utmp.h to add ut_tv (and a #include sys/time.h), write.exe
compiles and works...
cheers,
DaveK
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Re: On write command
On Jan 31 11:54, Dave Korn wrote:
On 31/01/2011 01:52, Larry Hall (Cygwin) wrote:
No, that's the correct place to search. If it's not showing up, none of
the current packages provide 'write'.
It's part of util-linux, but it's configured out of the build on Cygwin,
because it relies on a working utmp file to operate. Which we don't have.
Hmm, I'm in the middle of a gcc testrun right now and can't rebuild my DLL,
but I noticed a few interesting points about the code:
winsup/cygwin/include/utmpx.h
/* Must be kept in sync with struct utmp as defined in sys/utmp.h! */
struct utmpx
{
short ut_type;
pid_t ut_pid;
char ut_line[UT_LINESIZE];
char ut_id[UT_IDLEN];
time_t ut_time;
char ut_user[UT_NAMESIZE];
char ut_host[UT_HOSTSIZE];
long ut_addr;
struct timeval ut_tv;
};
winsup/cygwin/include/sys/utmp.h
struct utmp
{
short ut_type;
pid_t ut_pid;
char ut_line[UT_LINESIZE];
char ut_id[UT_IDLEN];
time_t ut_time;
char ut_user[UT_NAMESIZE];
char ut_host[UT_HOSTSIZE];
long ut_addr;
};
That could explain why successive calls to getutent() appear to lose frame
across the contents of utmp. Also,
winsup/cygwin/syscalls.cc
/* Note: do not make NO_COPY */
static struct utmp utmp_data_buf[16];
static unsigned utix = 0;
#define nutdbuf (sizeof (utmp_data_buf) / sizeof (utmp_data_buf[0]))
#define utmp_data ({ \
if (utix nutdbuf) \
utix = 0; \
utmp_data_buf + utix++; \
})
I haven't slept all night, but isn't that going to overrun by one? Anyway
with the fix to utmp.h to add ut_tv (and a #include sys/time.h), write.exe
compiles and works...
The utmp file is in the old utmp format for backward compatibility. The
utx functions are available and return a ut_tv field, but it's just
extracted from the utmp ut_time field at function call time. The right
thing to do for write is to have a autoconf test for the ut_tv field
and not using it, if it's not available.
In theory we should switch to a utmpx file at one point. When we do
this, we can also add the ut_addr_v6 field, which is missing so far.
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Project Co-Leader cygwin AT cygwin DOT com
Red Hat
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Re: On write command
On 31/01/2011 11:49, Corinna Vinschen wrote: The utmp file is in the old utmp format for backward compatibility. The utx functions are available and return a ut_tv field, but it's just extracted from the utmp ut_time field at function call time. The right thing to do for write is to have a autoconf test for the ut_tv field and not using it, if it's not available. Nah, I was mistaken. It actually works fine as-is. I was fooled by the way old utmp entries get the first char of the username NULled out into thinking it was getting bad data, but a quick login convinced me that write actually works just fine and all the util-linux maintainer needs do is add the configure option to enable building it. I still think that utmp_data macro is going to return utmp_data_buf[nutdbuf] at some point, though. Shouldn't it be if (utix = nutdbuf)? cheers, DaveK -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
Re: On write command
On Jan 31 13:28, Dave Korn wrote: I still think that utmp_data macro is going to return utmp_data_buf[nutdbuf] at some point, though. Shouldn't it be if (utix = nutdbuf)? Indeed. Thanks for catching. I fixed it in CVS. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Project Co-Leader cygwin AT cygwin DOT com Red Hat -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
Re: On write command
On 1/29/2011 8:20 AM, Angelo Graziosi wrote: I would ask if on Cygwin I can use the 'write' command: write - send a message to another user $ write USER [ttyname] I remember I have used it some years ago, but not remember if it was on GNU/Linux or Cygwin. I did a research on http://cygwin.com/packages and didn't find it, but perhaps I did the wrong search.. No, that's the correct place to search. If it's not showing up, none of the current packages provide 'write'. -- Larry _ A: Yes. Q: Are you sure? A: Because it reverses the logical flow of conversation. Q: Why is top posting annoying in email? -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
Re: On write command
On 1/29/11 5:20 AM, Angelo Graziosi wrote: I would ask if on Cygwin I can use the 'write' command: write - send a message to another user $ write USER [ttyname] I remember I have used it some years ago, but not remember if it was on GNU/Linux or Cygwin. I did a research on http://cygwin.com/packages and didn't find it, but perhaps I did the wrong search.. Even in other Unix environments, write(1) is seldom used these days. Windows *does* provide a way to send a message to other users using the msg command or net send. signature.asc Description: OpenPGP digital signature
