On Tue, 20 Dec 2022 14:58:54 +0100
tito via Dng <dng@???> wrote:

> On Tue, 20 Dec 2022 13:29:23 +0100
> aitor <aitor_czr@???> wrote:
>
> > Hi,
> >
> > In order to simplify the code of simple-netaid i'm trying to get the tty of a running process
> > using the struct `proc_t` declared the `procps` project:
> >
> > https://salsa.debian.org/debian/procps/-/blob/master/library/include/readproc.h
> >
> > Pay attention to the integer defined in the line nº 155:
> >
> >     int tty; // stat- full device number of controlling terminal
> >
> > This is indeed the value i'm trying to request, and a|ccording to the
> > comment done at the right of the variable ||containing the word *stat*, this is supposedly the flag to be passed to
> > openproc():|
> >
> > |https://manpages.debian.org/testing/procps/openproc.3.en.html
> > |
> >
> > |i.e. the flag PROC_FILLSTAT, as shown in the following C program:|
> >
> > |
> > |
> >
> > |______ MAIN.C _______
> > |
> >
> > |#include <stdio.h>
> > #include <stdlib.h>
> > #include <proc/readproc.h>
> >
> > int main(int argc, char **argv)
> > {
> >   proc_t *proc_info;|
> >
> > |PROCTAB *proc = openproc(PROC_FILLSTAT);
> >
> >   while(proc_info = readproc(proc, NULL)) {
> >
> >     if(proc_info->tgid == atoi(argv[1])) {
> >
> >        printf("/dev/pts/%d\n", proc_info->tty);
> >     }
> >
> >     freeproc(proc_info);
> >  }
> >
> >   closeproc(proc);|
> >
> > |return 0;
> > }
> > |
> >
> > |_______ END ________|
> >
> > |
> > |
> >
> > |You need to install libprocps-dev. Then, compile the program as follows:|
> >
> > |$ gcc main.c -o main -lprocps|
> >
> > |If you open a terminal and try to run the program passing the pid of
> > the process as argument in the command line, that is:|
> >
> > |$ ./main $(echo $$)|
> >
> > |It should print the tty of the current terminal, in the same way as tty
> > does:|
> >
> > |$ tty
> > /dev/pts/4
> > |
> >
> > |But this is what i'm getting instead:|
> >
> > |$ ./main $(echo $$)
> > /dev/pts/34820|
> >
>
> $$ is the process ID (PID) of the script itself.

tito@devuan:~$ echo $$
12170
tito@devuan:~$ tty
/dev/pts/0
tito@devuan:~$

>
> > |As you can see, a very high number. Whereas the printed value should be
> > equal to 4. If you try passing the pid of another running process,
> > you'll get similar results or zero. Any thoughts on what's wrong in the
> > program? |||May this be a bug in procps?| |
> >
> > |Thanks in advance,|
> >
> > |Aitor.|
> >
> > |
> > |
>
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