# Bug in Ruby's PTY extension

**URL:** <https://www.ruby-forum.com/t/bug-in-rubys-pty-extension/111313>\
**Category:** Ruby\
**Created:** [August 5, 2007, 7:30pm UTC](https://www.ruby-forum.com/t/bug-in-rubys-pty-extension/111313 "2007-08-05T19:30:25Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![ronald\_braswell](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f9ae1b/32.png) [@ronald\_braswell](https://www.ruby-forum.com/u/ronald_braswell)\
**Post date:** [August 5, 2007, 7:30pm UTC](https://www.ruby-forum.com/t/bug-in-rubys-pty-extension/111313/1 "2007-08-05T19:30:25Z")

</div>

I’m new to the ML so please forgive me if this has been discussed  
previously.

Ruby version: 1.8.5  
OS: Solaris 10 x64 (11/06)  
CPU: Dual core Opteron

When using expect or RExpect I was getting an intermittent premature  
EOFError on the first call to expect. Catching this exception and then  
going on was an ugly work around.

pty.c:

I noticed that Solaris 10 does not support TIOCSCTTY so in function  
establishShell() the child process closes the slave device and reopens  
it to  
force it to be the controlling tty. The parent process also closes the  
slave device because it does not need it. I added a call to nanosleep  
for  
20 milliseconds just before the parent process closes the slave fd at  
the  
end of establishShell() and I now both expect and RExpect work reliably.  
I  
suspect that just keeping a reference to the open file object in the  
parent  
process while the child process closes and reopens the slave device  
prevents  
the EOF from occurring – but I am far from an expert on Solaris  
internals.  
This may not be the best way to solve the problem and just adding the  
small  
delay does not ensure that the problem will never happen again but so  
far,  
so good.

Ron

---

<div class="post-metadata">

**Author:** ![ronald\_braswell](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f9ae1b/32.png) [@ronald\_braswell](https://www.ruby-forum.com/u/ronald_braswell)\
**Post date:** [August 6, 2007, 10:39am UTC](https://www.ruby-forum.com/t/bug-in-rubys-pty-extension/111313/2 "2007-08-06T10:39:36Z")

</div>

Hi,

At Mon, 6 Aug 2007 02:28:38 +0900,  
ronald braswell wrote in [ruby-talk:263410]:

> delay does not ensure that the problem will never happen again but so far,  
> so good.

Does this patch work?

# Index: ext/pty/expect\_sample.rb

— ext/pty/expect\_sample.rb (revision 12878)  
+++ ext/pty/expect\_sample.rb (working copy)  
@@ -16,8 +16,4 @@ PTY.spawn(“ftp [ftp.ruby-lang.org](http://ftp.ruby-lang.org)”) do |r  
$expect\_verbose = false

- r\_f.expect(/^Name.\*: /) do

- w\_f.print “ftp\n”

- end

- if !ENV[‘USER’].nil?  
username = ENV[‘USER’]  
@@ -28,9 +24,6 @@ PTY.spawn(“ftp [ftp.ruby-lang.org](http://ftp.ruby-lang.org)”) do |r  
end

- r\_f.expect(‘word:’) do

- w\_f.print username+“@\n”

- end

- r\_f.expect("\> ") do

- w\_f.print “cd pub/ruby\n”

- r\_f.expect(/^(Name).\*: |(word):|\> /) do
- w\_f.puts($1 ? “ftp” : $2 ? “#{username}@” : “cd pub/ruby”)  
end  
r\_f.expect("\> ") do  
Index: ext/pty/pty.c  
===================================================================  
— ext/pty/pty.c (revision 12878)  
+++ ext/pty/pty.c (working copy)  
@@ -40,8 +40,8 @@  
#if !defined(HAVE\_OPENPTY)  
#if defined(\_\_hpux)  
-static  
-char \*MasterDevice = “/dev/ptym/pty%s”,

- \*SlaveDevice = “/dev/pty/tty%s”,
- \*deviceNo[] = {  
+static const  
+char MasterDevice[] = “/dev/ptym/pty%s”,

- SlaveDevice[] = “/dev/pty/tty%s”,
- \*const deviceNo[] = {  
“p0”,“p1”,“p2”,“p3”,“p4”,“p5”,“p6”,“p7”,  
“p8”,“p9”,“pa”,“pb”,“pc”,“pd”,“pe”,“pf”,  
@@ -63,8 +63,8 @@ char _MasterDevice = “/dev/ptym/pty%s”,  
};  
 #elif defined(\_IBMESA) /_ AIX/ESA \*/  
-static  
-char \*MasterDevice = “/dev/ptyp%s”,

- \*SlaveDevice = “/dev/ttyp%s”,
- \*deviceNo[] = {  
+static const  
+char MasterDevice[] = “/dev/ptyp%s”,

- SlaveDevice[] = “/dev/ttyp%s”,
- \*const deviceNo[] = {  
“00”,“01”,“02”,“03”,“04”,“05”,“06”,“07”,“08”,“09”,“0a”,“0b”,“0c”,“0d”,“0e”,“0f”,  
“10”,“11”,“12”,“13”,“14”,“15”,“16”,“17”,“18”,“19”,“1a”,“1b”,“1c”,“1d”,“1e”,“1f”,  
@@ -85,8 +85,8 @@ char \*MasterDevice = “/dev/ptyp%s”,  
};  
#elif !defined(HAVE\_PTSNAME)  
-static  
-char \*MasterDevice = “/dev/pty%s”,

- \*SlaveDevice = “/dev/tty%s”,
- \*deviceNo[] = {  
+static const  
+char MasterDevice[] = “/dev/pty%s”,

- SlaveDevice[] = “/dev/tty%s”,
- \*const deviceNo[] = {  
“p0”,“p1”,“p2”,“p3”,“p4”,“p5”,“p6”,“p7”,  
“p8”,“p9”,“pa”,“pb”,“pc”,“pd”,“pe”,“pf”,  
@@ -102,6 +102,4 @@ char _MasterDevice = “/dev/pty%s”,  
 #endif /_ !defined(HAVE\_OPENPTY) \*/

## -static char SlaveName[DEVICELEN];

#ifndef HAVE\_SETEUID

# ifdef HAVE\_SETREUID

@@ -156,15 +154,13 @@ pty\_syswait(info)  
if (cpid == -1) return Qnil;

-#if defined(IF\_STOPPED)

- if (IF\_STOPPED(status)) { /\* suspend \*/
- 

```
 raise_from_wait("stopped", info);

```

- }  
-#elif defined(WIFSTOPPED)
- if (WIFSTOPPED(status)) { /\* suspend \*/
- 

```
 raise_from_wait("stopped", info);

```

- }  
+#if defined(WIFSTOPPED)  
+#elif defined(IF\_STOPPED)  
+#define WIFSTOPPED(status) IF\_STOPPED(status)  
#else  
----\>\> Either IF\_STOPPED or WIFSTOPPED is needed \<\<----  
#endif /\* WIFSTOPPED | IF\_STOPPED \*/

- if (WIFSTOPPED(status)) { /\* suspend \*/
- 

```
 raise_from_wait("stopped", info);

```

- }  
else if (kill(info-\>child\_pid, 0) == 0) {  
raise\_from\_wait(“changed”, info);  
@@ -177,5 +173,5 @@ pty\_syswait(info)  
}

-static void getDevice \_((int\*, int\*));  
+static void getDevice \_((int\*, int\*, char [DEVICELEN]));

struct exec\_info {  
@@ -195,11 +191,12 @@ pty\_exec(v)

static void  
-establishShell(argc, argv, info)  
+establishShell(argc, argv, info, SlaveName)  
int argc;  
VALUE \*argv;  
struct pty\_info \*info;

- char SlaveName[DEVICELEN];  
{  
int i,master,slave;

- char \*p,\*getenv();

- char \*p, tmp, \*getenv();  
struct passwd \*pwent;  
VALUE v;  
@@ -224,5 +221,5 @@ establishShell(argc, argv, info)  
argv = &v;  
}

- getDevice(&master,&slave);

- getDevice(&master, &slave, SlaveName);

- write(slave, “”, 1);  
dup2(slave,0);  
dup2(slave,1);  
@@ -289,4 +287,5 @@ establishShell(argc, argv, info)  
}

- read(master, &tmp, 1);  
close(slave);

@@ -306,6 +305,7 @@ pty\_finalize\_syswait(info)

static int  
-get\_device\_once(master, slave, fail)  
+get\_device\_once(master, slave, SlaveName, fail)  
int \*master, \*slave, fail;

- char SlaveName[DEVICELEN];  
{  
#if defined HAVE\_OPENPTY  
@@ -354,4 +354,5 @@ get\_device\_once(master, slave, fail)  
if(ioctl(j, I\_PUSH, “ptem”) != -1) {  
if(ioctl(j, I\_PUSH, “ldterm”) != -1) {
- 

```
   ioctl(j, I_PUSH, "ttcompat");

```

#endif  
\*master = i;  
@@ -396,10 +397,11 @@ get\_device\_once(master, slave, fail)

static void  
-getDevice(master, slave)  
+getDevice(master, slave, SlaveName)  
int \*master, \*slave;

- char SlaveName[DEVICELEN];  
{

- if (get\_device\_once(master, slave, 0)) {

- if (get\_device\_once(master, slave, SlaveName, 0)) {  
rb\_gc();

- get\_device\_once(master, slave, 1);

- get\_device\_once(master, slave, SlaveName, 1);  
}  
}  
@@ -418,9 +420,10 @@ pty\_getpty(argc, argv, self)  
VALUE rport = rb\_obj\_alloc(rb\_cFile);  
VALUE wport = rb\_obj\_alloc(rb\_cFile);

- char SlaveName[DEVICELEN];

- establishShell(argc, argv, &info);

- establishShell(argc, argv, &info, SlaveName);

---

<div class="post-metadata">

**Author:** ![ronald\_braswell](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f9ae1b/32.png) [@ronald\_braswell](https://www.ruby-forum.com/u/ronald_braswell)\
**Post date:** [August 6, 2007, 6:28pm UTC](https://www.ruby-forum.com/t/bug-in-rubys-pty-extension/111313/3 "2007-08-06T18:28:48Z")

</div>

> > I noticed that Solaris 10 does not support TIOCSCTTY so in function  
> > parent  
> > Does this patch work?
> 
> - w\_f.print “ftp\n”
> - r\_f.expect("\> ") do  
> #if !defined(HAVE\_OPENPTY)  
> “p8”,“p9”,“pa”,“pb”,“pc”,“pd”,“pe”,“pf”,
> 
> - \*const deviceNo[] = {
> 
> - \*deviceNo[] = {
> - 
> - if (WIFSTOPPED(status)) { /\* suspend \*/
> 
> - }
> 
> - char \*p, tmp, \*getenv();  
> close(master);  
> @@ -306,6 +305,7 @@ pty\_finalize\_syswait(info)  
> if(ioctl(j, I\_PUSH, “ldterm”) != -1) {  
> {
> 
> - char SlaveName[DEVICELEN];  
> –  
> Nobu Nakada

Hi Nobu,

Thanks for your patch. It is much better than the quick hack that I had  
done. I have tested it and it works fine! Just one thing, I had to  
comment  
out freeDevice() in my version of pty.c since it referenced the  
previously  
file scoped SlaveName. freeDevice() was not externally linked and there  
were no references to it in pty.c. Maybe I overlooked the deletion of  
it  
in you diff -u output.

Ron

---

<div class="post-metadata">

**Author:** ![ronald\_braswell](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f9ae1b/32.png) [@ronald\_braswell](https://www.ruby-forum.com/u/ronald_braswell)\
**Post date:** [August 6, 2007, 6:56pm UTC](https://www.ruby-forum.com/t/bug-in-rubys-pty-extension/111313/4 "2007-08-06T18:56:50Z")

</div>

Hi,

In message “Re: Bug in Ruby’s PTY extension”  
on Mon, 6 Aug 2007 17:38:17 +0900, Nobuyoshi N.  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes:

|Does this patch work?

|— ext/pty/expect\_sample.rb (revision 12878)  
|+++ ext/pty/expect\_sample.rb (working copy)

Can you commit please?

```
          matz.

```

---

<div class="post-metadata">

**Author:** ![ronald\_braswell](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f9ae1b/32.png) [@ronald\_braswell](https://www.ruby-forum.com/u/ronald_braswell)\
**Post date:** [August 7, 2007, 8:00am UTC](https://www.ruby-forum.com/t/bug-in-rubys-pty-extension/111313/5 "2007-08-07T08:00:04Z")

</div>

Hi,

At Tue, 7 Aug 2007 01:28:08 +0900,  
ronald braswell wrote in [ruby-talk:263528]:

> Thanks for your patch. It is much better than the quick hack that I had  
> done. I have tested it and it works fine! Just one thing, I had to comment  
> out freeDevice() in my version of pty.c since it referenced the previously  
> file scoped SlaveName. freeDevice() was not externally linked and there  
> were no references to it in pty.c. Maybe I overlooked the deletion of it  
> in you diff -u output.

It has been deleted in 1.8.6 already, since it wasn’t used at  
all.

---

<div class="post-metadata">

**Author:** ![ronald\_braswell](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/f9ae1b/32.png) [@ronald\_braswell](https://www.ruby-forum.com/u/ronald_braswell)\
**Post date:** [August 6, 2007, 4:20pm UTC](https://www.ruby-forum.com/t/bug-in-rubys-pty-extension/111313/6 "2007-08-06T16:20:22Z")

</div>

On Aug 5, 11:28 am, “ronald braswell” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> the EOF from occurring – but I am far from an expert on Solaris internals.  
> This may not be the best way to solve the problem and just adding the small  
> delay does not ensure that the problem will never happen again but so far,  
> so good.

This quote from comp.programming may be useful:

"In System V, the controlling terminal is the first tty that’s opened  
that is not already associated with a session. If you don’t want that  
tty to be the controlling terminal, use the O\_NOCTTY flag on open().

You don’t need the TIOCSCTTY ioctl in SVR4 systems."

[http://tinyurl.com/2af8ob](http://tinyurl.com/2af8ob)

Regards,

Dan