How can we find out the pseudoterminal master and slave from each other?
A pseudoterminal has a pair of master and slave.
How can we find out the master device file from a slave device file (e.g. /etc/pts/3)? I only find /dev/ptmx and /dev/pts/ptmx, but they can't be shared by multiple slaves.
Given one of the processes working on the master and slave, how can we find out the other?
For example, ps provides information about the controlling tty of each process. Can it be helpful?
Thanks.
linux pseudoterminal
edited 8 hours ago
Stephen Kitt
164k24366445
asked 9 hours ago
Tim
26.1k74246455
add a comment |
A pseudoterminal has a pair of master and slave.
How can we find out the master device file from a slave device file (e.g. /etc/pts/3)? I only find /dev/ptmx and /dev/pts/ptmx, but they can't be shared by multiple slaves.
Given one of the processes working on the master and slave, how can we find out the other?
For example, ps provides information about the controlling tty of each process. Can it be helpful?
Thanks.
linux pseudoterminal
edited 8 hours ago
Stephen Kitt
164k24366445
asked 9 hours ago
Tim
26.1k74246455
2
Possible duplicate of Are all the slaves paired with the same master?
– JdeBP
8 hours ago
add a comment |
A pseudoterminal has a pair of master and slave.
How can we find out the master device file from a slave device file (e.g. /etc/pts/3)? I only find /dev/ptmx and /dev/pts/ptmx, but they can't be shared by multiple slaves.
Given one of the processes working on the master and slave, how can we find out the other?
For example, ps provides information about the controlling tty of each process. Can it be helpful?
Thanks.
linux pseudoterminal
edited 8 hours ago
Stephen Kitt
164k24366445
asked 9 hours ago
Tim
26.1k74246455
A pseudoterminal has a pair of master and slave.
How can we find out the master device file from a slave device file (e.g. /etc/pts/3)? I only find /dev/ptmx and /dev/pts/ptmx, but they can't be shared by multiple slaves.
Given one of the processes working on the master and slave, how can we find out the other?
For example, ps provides information about the controlling tty of each process. Can it be helpful?
Thanks.
linux pseudoterminal
linux pseudoterminal
edited 8 hours ago
Stephen Kitt
164k24366445
asked 9 hours ago
Tim
26.1k74246455
edited 8 hours ago
Stephen Kitt
164k24366445
asked 9 hours ago
Tim
26.1k74246455
edited 8 hours ago
Stephen Kitt
164k24366445
edited 8 hours ago
Stephen Kitt
164k24366445
edited 8 hours ago
Stephen Kitt
164k24366445
164k24366445
asked 9 hours ago
Tim
26.1k74246455
asked 9 hours ago
Tim
26.1k74246455
asked 9 hours ago
Tim
26.1k74246455
26.1k74246455
2
Possible duplicate of Are all the slaves paired with the same master?
– JdeBP
8 hours ago
add a comment |
2
Possible duplicate of Are all the slaves paired with the same master?
– JdeBP
8 hours ago
2
2
Possible duplicate of Are all the slaves paired with the same master?
– JdeBP
8 hours ago
Possible duplicate of Are all the slaves paired with the same master?
– JdeBP
8 hours ago
add a comment |
2 Answers
2
active
oldest
votes
On Linux, using devpts, there is no master device file. The process on the master end uses a file descriptor, which it gets by opening ptmx, but there’s no corresponding device node.
See the ptmx manpage for details.
(With BSD-style ptys on Linux, there are matching device pairs, such as /dev/ptyp1 and /dev/ttyp1, respectively on the master and slave side.)
answered 8 hours ago
Stephen Kitt
164k24366445
add a comment |
That is one thing that is harder than it should be.
With newer kernels, the index of the slave pty paired with a master can be gathered from the tty-index entry from /proc/PID/fdinfo/FD. See this commit.
When that hits the stores it will be easy to do a find /proc -lname /dev/ptmx to get a list of processes holding a handle to a master pty, get the index from each of them, and then do another find -lname /dev/pts/INDEX to find all processes that hold a handle to the slave pty.
With older kernels, the only way you can get that is by attaching with a debugger to a process holding a master pty, and call ptsname(3) on the file descriptor.
answered 6 hours ago
mosvy
6,1411425
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
On Linux, using devpts, there is no master device file. The process on the master end uses a file descriptor, which it gets by opening ptmx, but there’s no corresponding device node.
See the ptmx manpage for details.
(With BSD-style ptys on Linux, there are matching device pairs, such as /dev/ptyp1 and /dev/ttyp1, respectively on the master and slave side.)
answered 8 hours ago
Stephen Kitt
164k24366445
add a comment |
On Linux, using devpts, there is no master device file. The process on the master end uses a file descriptor, which it gets by opening ptmx, but there’s no corresponding device node.
See the ptmx manpage for details.
(With BSD-style ptys on Linux, there are matching device pairs, such as /dev/ptyp1 and /dev/ttyp1, respectively on the master and slave side.)
answered 8 hours ago
Stephen Kitt
164k24366445
add a comment |
On Linux, using devpts, there is no master device file. The process on the master end uses a file descriptor, which it gets by opening ptmx, but there’s no corresponding device node.
See the ptmx manpage for details.
(With BSD-style ptys on Linux, there are matching device pairs, such as /dev/ptyp1 and /dev/ttyp1, respectively on the master and slave side.)
answered 8 hours ago
Stephen Kitt
164k24366445
On Linux, using devpts, there is no master device file. The process on the master end uses a file descriptor, which it gets by opening ptmx, but there’s no corresponding device node.
See the ptmx manpage for details.
(With BSD-style ptys on Linux, there are matching device pairs, such as /dev/ptyp1 and /dev/ttyp1, respectively on the master and slave side.)
answered 8 hours ago
Stephen Kitt
164k24366445
edited 8 hours ago
answered 8 hours ago
Stephen Kitt
164k24366445
answered 8 hours ago
Stephen Kitt
164k24366445
answered 8 hours ago
Stephen Kitt
164k24366445
164k24366445
add a comment |
add a comment |
That is one thing that is harder than it should be.
With newer kernels, the index of the slave pty paired with a master can be gathered from the tty-index entry from /proc/PID/fdinfo/FD. See this commit.
When that hits the stores it will be easy to do a find /proc -lname /dev/ptmx to get a list of processes holding a handle to a master pty, get the index from each of them, and then do another find -lname /dev/pts/INDEX to find all processes that hold a handle to the slave pty.
With older kernels, the only way you can get that is by attaching with a debugger to a process holding a master pty, and call ptsname(3) on the file descriptor.
answered 6 hours ago
mosvy
6,1411425
add a comment |
That is one thing that is harder than it should be.
With newer kernels, the index of the slave pty paired with a master can be gathered from the tty-index entry from /proc/PID/fdinfo/FD. See this commit.
When that hits the stores it will be easy to do a find /proc -lname /dev/ptmx to get a list of processes holding a handle to a master pty, get the index from each of them, and then do another find -lname /dev/pts/INDEX to find all processes that hold a handle to the slave pty.
With older kernels, the only way you can get that is by attaching with a debugger to a process holding a master pty, and call ptsname(3) on the file descriptor.
answered 6 hours ago
mosvy
6,1411425
add a comment |
That is one thing that is harder than it should be.
With newer kernels, the index of the slave pty paired with a master can be gathered from the tty-index entry from /proc/PID/fdinfo/FD. See this commit.
When that hits the stores it will be easy to do a find /proc -lname /dev/ptmx to get a list of processes holding a handle to a master pty, get the index from each of them, and then do another find -lname /dev/pts/INDEX to find all processes that hold a handle to the slave pty.
With older kernels, the only way you can get that is by attaching with a debugger to a process holding a master pty, and call ptsname(3) on the file descriptor.
answered 6 hours ago
mosvy
6,1411425
That is one thing that is harder than it should be.
With newer kernels, the index of the slave pty paired with a master can be gathered from the tty-index entry from /proc/PID/fdinfo/FD. See this commit.
When that hits the stores it will be easy to do a find /proc -lname /dev/ptmx to get a list of processes holding a handle to a master pty, get the index from each of them, and then do another find -lname /dev/pts/INDEX to find all processes that hold a handle to the slave pty.
With older kernels, the only way you can get that is by attaching with a debugger to a process holding a master pty, and call ptsname(3) on the file descriptor.
answered 6 hours ago
mosvy
6,1411425
answered 6 hours ago
mosvy
6,1411425
answered 6 hours ago
mosvy
6,1411425
answered 6 hours ago
mosvy
6,1411425
6,1411425
add a comment |
add a comment |
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2
Possible duplicate of Are all the slaves paired with the same master?
– JdeBP
8 hours ago