Bug #9144: ptys on AIX version 4 through 7

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.0.0p247 (2013-06-27 revision 41674) [powerpc-aix6.1.0.0]
• Backport: 2.0.0: REQUIRED, 2.1: DONE, 2.2: DONE

[pedz (Perry Smith)]

The best way to open a pty on AIX version 4 through 7 is using what they call "AT&T" mode. The steps are to first open "/dev/ptc" which opens the master side. Then to a ttyname on the file descriptor and open the string that is returned to open the slave side.

cat q.c
#include <stdio.h>
#include <fcntl.h>

int main(int argc, char *argv[])
{
int master = open("/dev/ptc", O_RDWR);
char *slave_name = ttyname(master);
int slave = open(slave_name, O_RDWR);
int n;
char buf[128];

printf("slave name is %s\n", slave_name);
printf("master fd is %d, slave fd is %d\n", master, slave);
write(master, "blah\n", 5);
n = read(slave, buf, sizeof(buf));
printf("n = %d\n", n);
printf("%*.s", n, n, buf);
write(slave, "foodog\n", 7);
n = read(master, buf, sizeof(buf));
printf("n = %d\n", n);
printf("%.*s", n, n, buf);
return 0;
}

make q
cc q.c -o q

./q
slave name is /dev/pts/9
master fd is 3, slave fd is 5
n = 5
blah
n = 14
blah
foodog

(Note that ECHO is set on the tty which is why we see 'blah' when the slave is read.)

You can also use what the ruby code calls BSD 4.2 ptys. On my build that I did as simply as possible, I'm not sure which code I got but it is not working. I have several versions of Ruby and all fail with "can't get Master/Slave device (RuntimeError)" While "BSD" mode is supported and works, the "AT&T" mode is much nicer.

For AIX version 3, there was a similar approach but instead of /dev/ptc, the master was called /dev/ptm.

The _IBMESA code in ext/pty/pty.c (which mentions AIX) I don't recognize those names.

There is no need to push any streams modules, etc. Everything is autopushed. You might want to add in a grantpt but I'm still not clear when and if that is needed.

• File signature.asc signature.asc added

Doing more research, the existing ruby code is 99% there.

I got it to work by changing line 248 of ext/pty/pty.c from:

#if defined(I_PUSH) && !defined(linux)

to

#if defined(I_PUSH) && !defined(linux) && !defined(_AIX)

AIX has autopush which is really what the second half of the && should be testing.

Perry

On Nov 23, 2013, at 1:14 PM, pedz (Perry Smith) [e-mail] wrote:

Issue #9144 has been reported by pedz (Perry Smith).

---

Bug #9144: ptys on AIX version 4 through 7
https://bugs.ruby-lang.org/issues/9144

Author: pedz (Perry Smith)
Status: Open
Priority: Normal
Assignee:
Category:
Target version:
ruby -v: ruby 2.0.0p247 (2013-06-27 revision 41674) [powerpc-aix6.1.0.0]
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN

The best way to open a pty on AIX version 4 through 7 is using what they call "AT&T" mode. The steps are to first open "/dev/ptc" which opens the master side. Then to a ttyname on the file descriptor and open the string that is returned to open the slave side.

cat q.c
#include <stdio.h>
#include <fcntl.h>

int main(int argc, char *argv[])
{
int master = open("/dev/ptc", O_RDWR);
char *slave_name = ttyname(master);
int slave = open(slave_name, O_RDWR);
int n;
char buf[128];

printf("slave name is %s\n", slave_name);
printf("master fd is %d, slave fd is %d\n", master, slave);
write(master, "blah\n", 5);
n = read(slave, buf, sizeof(buf));
printf("n = %d\n", n);
printf("%*.s", n, n, buf);
write(slave, "foodog\n", 7);
n = read(master, buf, sizeof(buf));
printf("n = %d\n", n);
printf("%.*s", n, n, buf);
return 0;
}

make q
cc q.c -o q

./q
slave name is /dev/pts/9
master fd is 3, slave fd is 5
n = 5
blah
n = 14
blah
foodog

(Note that ECHO is set on the tty which is why we see 'blah' when the slave is read.)

You can also use what the ruby code calls BSD 4.2 ptys. On my build that I did as simply as possible, I'm not sure which code I got but it is not working. I have several versions of Ruby and all fail with "can't get Master/Slave device (RuntimeError)" While "BSD" mode is supported and works, the "AT&T" mode is much nicer.

For AIX version 3, there was a similar approach but instead of /dev/ptc, the master was called /dev/ptm.

The _IBMESA code in ext/pty/pty.c (which mentions AIX) I don't recognize those names.

There is no need to push any streams modules, etc. Everything is autopushed. You might want to add in a grantpt but I'm still not clear when and if that is needed.

--
http://bugs.ruby-lang.org/

• Status changed from Open to Closed
• % Done changed from 0 to 100

Applied in changeset r49776.

---

• ext/pty/pty.c: AIX supports autopush. Patch by Perry Smith [ruby-core:58539] [Bug #9144]

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 1.9.3: UNKNOWN, 2.0.0: UNKNOWN to 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: REQUIRED to 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: DONE

Backported into ruby_2_2 branch at r50564.

[usa (Usaku NAKAMURA)]

• Backport changed from 2.0.0: REQUIRED, 2.1: REQUIRED, 2.2: DONE to 2.0.0: REQUIRED, 2.1: DONE, 2.2: DONE

ruby_2_1 r50570 merged revision(s) 49776.