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Two process with identical PID after a fork call
After fork(), where does the child begin its execution?Why is the PGID of my child processes not the PID of the parent?Process's father after setpgid(0,0);what does it mean 'fork()' will copy address space of original processHow does fork system call really worksWhy is process not part of expected process group?Process and fork() MethodIs a session leader the only process in its group?fork() and COW behavior after exec()Question about global environment variables and fork() & exec()
According to the fork documentation (man 2 fork):
The child process is an exact duplicate of the parent process except for the following points:
- The child has its own unique process ID, and this PID does not match the ID of any existing process group (setpgid(2)).
So, does it means that two process belonging to two different process groups can have a same PID? It makes no sense to me but fork enforces that no new PID equals no existing PGID, and thus there could be a non-group leader process with same PID that the newly created process by fork, isn't?
process fork
asked yesterday
Peregring-lkPeregring-lk
280213
add a comment |
According to the fork documentation (man 2 fork):
The child process is an exact duplicate of the parent process except for the following points:
- The child has its own unique process ID, and this PID does not match the ID of any existing process group (setpgid(2)).
So, does it means that two process belonging to two different process groups can have a same PID? It makes no sense to me but fork enforces that no new PID equals no existing PGID, and thus there could be a non-group leader process with same PID that the newly created process by fork, isn't?
process fork
asked yesterday
Peregring-lkPeregring-lk
280213
2
From your quoted text: The child has its own unique process ID
– Kusalananda♦
yesterday
1
No, it means that the PID of a process cannot be equal to the PGID of a process group other than the one it's member of. Notice that process groups can become orphaned when the pg leader terminates -- the PID of the pg leader will not be reused as long as there are still processes with their PGID equal to it.
– mosvy
yesterday
1
@Kusalananda ouch stupid question then. I was confused because of the rest of the sentence.
– Peregring-lk
yesterday
add a comment |
According to the fork documentation (man 2 fork):
The child process is an exact duplicate of the parent process except for the following points:
- The child has its own unique process ID, and this PID does not match the ID of any existing process group (setpgid(2)).
So, does it means that two process belonging to two different process groups can have a same PID? It makes no sense to me but fork enforces that no new PID equals no existing PGID, and thus there could be a non-group leader process with same PID that the newly created process by fork, isn't?
process fork
asked yesterday
Peregring-lkPeregring-lk
280213
According to the fork documentation (man 2 fork):
The child process is an exact duplicate of the parent process except for the following points:
- The child has its own unique process ID, and this PID does not match the ID of any existing process group (setpgid(2)).
So, does it means that two process belonging to two different process groups can have a same PID? It makes no sense to me but fork enforces that no new PID equals no existing PGID, and thus there could be a non-group leader process with same PID that the newly created process by fork, isn't?
process fork
process fork
asked yesterday
Peregring-lkPeregring-lk
280213
asked yesterday
Peregring-lkPeregring-lk
280213
asked yesterday
Peregring-lkPeregring-lk
280213
asked yesterday
Peregring-lkPeregring-lk
280213
asked yesterday
Peregring-lkPeregring-lk
280213
280213
2
From your quoted text: The child has its own unique process ID
– Kusalananda♦
yesterday
1
No, it means that the PID of a process cannot be equal to the PGID of a process group other than the one it's member of. Notice that process groups can become orphaned when the pg leader terminates -- the PID of the pg leader will not be reused as long as there are still processes with their PGID equal to it.
– mosvy
yesterday
1
@Kusalananda ouch stupid question then. I was confused because of the rest of the sentence.
– Peregring-lk
yesterday
add a comment |
2
From your quoted text: The child has its own unique process ID
– Kusalananda♦
yesterday
1
No, it means that the PID of a process cannot be equal to the PGID of a process group other than the one it's member of. Notice that process groups can become orphaned when the pg leader terminates -- the PID of the pg leader will not be reused as long as there are still processes with their PGID equal to it.
– mosvy
yesterday
1
@Kusalananda ouch stupid question then. I was confused because of the rest of the sentence.
– Peregring-lk
yesterday
2
2
From your quoted text: The child has its own unique process ID
– Kusalananda♦
yesterday
From your quoted text: The child has its own unique process ID
– Kusalananda♦
yesterday
1
1
No, it means that the PID of a process cannot be equal to the PGID of a process group other than the one it's member of. Notice that process groups can become orphaned when the pg leader terminates -- the PID of the pg leader will not be reused as long as there are still processes with their PGID equal to it.
– mosvy
yesterday
No, it means that the PID of a process cannot be equal to the PGID of a process group other than the one it's member of. Notice that process groups can become orphaned when the pg leader terminates -- the PID of the pg leader will not be reused as long as there are still processes with their PGID equal to it.
– mosvy
yesterday
1
1
@Kusalananda ouch stupid question then. I was confused because of the rest of the sentence.
– Peregring-lk
yesterday
@Kusalananda ouch stupid question then. I was confused because of the rest of the sentence.
– Peregring-lk
yesterday
add a comment |
1 Answer
1
active
oldest
votes
Process IDs are unique.
Per the POSIX fork() documentation:
DESCRIPTION
The fork() function shall create a new process. The new process (child
process) shall be an exact copy of the calling process (parent
process) except as detailed below:
- The child process shall have a unique process ID.
- The child process ID also shall not match any active process group ID.
- The child process shall have a different parent process ID, which shall be the process ID of the calling process.
...
answered yesterday
Andrew HenleAndrew Henle
2,787911
add a comment |
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Process IDs are unique.
Per the POSIX fork() documentation:
DESCRIPTION
The fork() function shall create a new process. The new process (child
process) shall be an exact copy of the calling process (parent
process) except as detailed below:
- The child process shall have a unique process ID.
- The child process ID also shall not match any active process group ID.
- The child process shall have a different parent process ID, which shall be the process ID of the calling process.
...
answered yesterday
Andrew HenleAndrew Henle
2,787911
add a comment |
Process IDs are unique.
Per the POSIX fork() documentation:
DESCRIPTION
The fork() function shall create a new process. The new process (child
process) shall be an exact copy of the calling process (parent
process) except as detailed below:
- The child process shall have a unique process ID.
- The child process ID also shall not match any active process group ID.
- The child process shall have a different parent process ID, which shall be the process ID of the calling process.
...
answered yesterday
Andrew HenleAndrew Henle
2,787911
add a comment |
Process IDs are unique.
Per the POSIX fork() documentation:
DESCRIPTION
The fork() function shall create a new process. The new process (child
process) shall be an exact copy of the calling process (parent
process) except as detailed below:
- The child process shall have a unique process ID.
- The child process ID also shall not match any active process group ID.
- The child process shall have a different parent process ID, which shall be the process ID of the calling process.
...
answered yesterday
Andrew HenleAndrew Henle
2,787911
Process IDs are unique.
Per the POSIX fork() documentation:
DESCRIPTION
The fork() function shall create a new process. The new process (child
process) shall be an exact copy of the calling process (parent
process) except as detailed below:
- The child process shall have a unique process ID.
- The child process ID also shall not match any active process group ID.
- The child process shall have a different parent process ID, which shall be the process ID of the calling process.
...
answered yesterday
Andrew HenleAndrew Henle
2,787911
answered yesterday
Andrew HenleAndrew Henle
2,787911
answered yesterday
Andrew HenleAndrew Henle
2,787911
answered yesterday
Andrew HenleAndrew Henle
2,787911
2,787911
add a comment |
add a comment |
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2
From your quoted text: The child has its own unique process ID
– Kusalananda♦
yesterday
1
No, it means that the PID of a process cannot be equal to the PGID of a process group other than the one it's member of. Notice that process groups can become orphaned when the pg leader terminates -- the PID of the pg leader will not be reused as long as there are still processes with their PGID equal to it.
– mosvy
yesterday
1
@Kusalananda ouch stupid question then. I was confused because of the rest of the sentence.
– Peregring-lk
yesterday