openproc, closeproc - initialize process information from /proc/

       The behaviour of openproc is controlled by the following set of flags, which may be ORed together.  There
       are  three different kinds of flags. The first group of flags determines which information gets read from
       /proc/#pid for each process. The second group of flags (of which only one can be enacted  for  a  opendir
       call)  restricts which processes information is read for by providing a list of criteria. The third group
       of flags restricts this as well, but doesn't need arguments. These may be used together again.

       PROC_FILLMEM
            read information from /proc/#pid/statmPROC_FILLCOM
            allocate cmdline part of proc_t and read information from /proc/#pid/cmdlinePROC_FILLENV
            allocate environ part of proc_t and read information from /proc/#pid/environPROC_FILLUSR
            resolve user ids to names via /etc/passwdPROC_FILLGRP
            resolve group ids to names via /etc/groupPROC_FILLSTATUS
            read information from /proc/#pid/statusPROC_FILLSTAT
            read information from /proc/#pid/statPROC_FILLARG
            equivalent to PROC_FILLCOM

       PROC_FILLCGROUP
            alloc and fill in cgroup

       PROC_FILLSUPGRP
            resolve supplementary group id -> group name

       PROC_FILLOOM
            fill in proc_t oom_score and oom_adj

       PROC_FILLNS
            fill in proc_t namespace information

       PROC_FILLSYSTEMD
            fill in proc_t systemd information

       PROC_LOOSE_TASKS
            threat threads as if they were processes

       PROC_PID (2nd argument pid_t*pidlist)
            lookup only processes whose pid is contained in pidlist (the list is terminated with 0)

       PROC_UID (arguments uid_t*uidlist,intn)
            lookup only processes whose user id is contained in uidlist (where n is the number of uids contained
            in the list)

       PROC_EDITCGRPCVT
            edit cgroup as single vector

       PROC_EDITCMDLCVT
            edit cmdline as single vector

       PROC_EDITENVRCVT
            edit environ as single vector

       openproc, closeproc  - initialize process information from /proc/

       Only one of the flags needing additional arguments (PROC_{PID,UID}) may be used at a time.

       Please send bug reports to procps@freelists.org

Linux Manpage                                     14 July 2014                                       OPENPROC(3)

openproc  returns  a  pointer to a PROCTAB structure, or NULL if an error occurs. This usually means that
       /proc cannot be read by the process.

readproc(3), readproctab(3), /proc/, /usr/include/proc/readproc.h,

       The openproc function initializes a PROCTAB structure which can be used by iterated readproc calls to get
       information on current processes. Depending on flags, openproc may need a second argument or a second and
       third argument (see below).

       closeproc closes all files opened by openproc and deallocates the memory allocated by openproc.

       The PROCTAB structure is defined in <proc/readproc.h>