what are the meaning of values at proc/[pid]/stat?

Question

I was trying to develop an app to get CPU usage per app and kill apps when consuming much CPU. But I couldn't figure out how to do this.

I have read this post and have seen this answer. So I looked at proc/[pid]/stat. There are a lot of numeric values, but I couldn't understand which value is representing what.

Can anyone explain the meaning of values at proc/[pid]/stat..?

Answer 1

From man proc(5):

   /proc/[pid]/stat           Status information about the process.  This is used by ps(1).           It is defined in the kernel source file fs/proc/array.c.            The fields, in order, with their proper scanf(3) format speci‐           fiers, are listed below.  Whether or not certain of these           fields display valid information is governed by a ptrace           access mode PTRACE_MODE_READ_FSCREDS | PTRACE_MODE_NOAUDIT           check (refer to ptrace(2)).  If the check denies access, then           the field value is displayed as 0.  The affected fields are           indicated with the marking [PT].            (1) pid  %d                     The process ID.            (2) comm  %s                     The filename of the executable, in parentheses.                     This is visible whether or not the executable is                     swapped out.            (3) state  %c                     One of the following characters, indicating process                     state:                      R  Running                      S  Sleeping in an interruptible wait                      D  Waiting in uninterruptible disk sleep                      Z  Zombie                      T  Stopped (on a signal) or (before Linux 2.6.33)                        trace stopped                      t  Tracing stop (Linux 2.6.33 onward)                      W  Paging (only before Linux 2.6.0)                      X  Dead (from Linux 2.6.0 onward)                      x  Dead (Linux 2.6.33 to 3.13 only)                      K  Wakekill (Linux 2.6.33 to 3.13 only)                      W  Waking (Linux 2.6.33 to 3.13 only)                      P  Parked (Linux 3.9 to 3.13 only)            (4) ppid  %d                     The PID of the parent of this process.            (5) pgrp  %d                     The process group ID of the process.            (6) session  %d                     The session ID of the process.            (7) tty_nr  %d                     The controlling terminal of the process.  (The minor                     device number is contained in the combination of                     bits 31 to 20 and 7 to 0; the major device number is                     in bits 15 to 8.)            (8) tpgid  %d                     The ID of the foreground process group of the con‐                     trolling terminal of the process.            (9) flags  %u                     The kernel flags word of the process.  For bit mean‐                     ings, see the PF_* defines in the Linux kernel                     source file include/linux/sched.h.  Details depend                     on the kernel version.                      The format for this field was %lu before Linux 2.6.            (10) minflt  %lu                     The number of minor faults the process has made                     which have not required loading a memory page from                     disk.            (11) cminflt  %lu                     The number of minor faults that the process's                     waited-for children have made.            (12) majflt  %lu                     The number of major faults the process has made                     which have required loading a memory page from disk.            (13) cmajflt  %lu                     The number of major faults that the process's                     waited-for children have made.            (14) utime  %lu                     Amount of time that this process has been scheduled                     in user mode, measured in clock ticks (divide by                     sysconf(_SC_CLK_TCK)).  This includes guest time,                     guest_time (time spent running a virtual CPU, see                     below), so that applications that are not aware of                     the guest time field do not lose that time from                     their calculations.            (15) stime  %lu                     Amount of time that this process has been scheduled                     in kernel mode, measured in clock ticks (divide by                     sysconf(_SC_CLK_TCK)).            (16) cutime  %ld                     Amount of time that this process's waited-for chil‐                     dren have been scheduled in user mode, measured in                     clock ticks (divide by sysconf(_SC_CLK_TCK)).  (See                     also times(2).)  This includes guest time,                     cguest_time (time spent running a virtual CPU, see                     below).            (17) cstime  %ld                     Amount of time that this process's waited-for chil‐                     dren have been scheduled in kernel mode, measured in                     clock ticks (divide by sysconf(_SC_CLK_TCK)).            (18) priority  %ld                     (Explanation for Linux 2.6) For processes running a                     real-time scheduling policy (policy below; see                     sched_setscheduler(2)), this is the negated schedul‐                     ing priority, minus one; that is, a number in the                     range -2 to -100, corresponding to real-time priori‐                     ties 1 to 99.  For processes running under a non-                     real-time scheduling policy, this is the raw nice                     value (setpriority(2)) as represented in the kernel.                     The kernel stores nice values as numbers in the                     range 0 (high) to 39 (low), corresponding to the                     user-visible nice range of -20 to 19.                      Before Linux 2.6, this was a scaled value based on                     the scheduler weighting given to this process.            (19) nice  %ld                     The nice value (see setpriority(2)), a value in the                     range 19 (low priority) to -20 (high priority).            (20) num_threads  %ld                     Number of threads in this process (since Linux 2.6).                     Before kernel 2.6, this field was hard coded to 0 as                     a placeholder for an earlier removed field.            (21) itrealvalue  %ld                     The time in jiffies before the next SIGALRM is sent                     to the process due to an interval timer.  Since ker‐                     nel 2.6.17, this field is no longer maintained, and                     is hard coded as 0.            (22) starttime  %llu                     The time the process started after system boot.  In                     kernels before Linux 2.6, this value was expressed                     in jiffies.  Since Linux 2.6, the value is expressed                     in clock ticks (divide by sysconf(_SC_CLK_TCK)).                      The format for this field was %lu before Linux 2.6.            (23) vsize  %lu                     Virtual memory size in bytes.            (24) rss  %ld                     Resident Set Size: number of pages the process has                     in real memory.  This is just the pages which count                     toward text, data, or stack space.  This does not                     include pages which have not been demand-loaded in,                     or which are swapped out.            (25) rsslim  %lu                     Current soft limit in bytes on the rss of the                     process; see the description of RLIMIT_RSS in                     getrlimit(2).            (26) startcode  %lu  [PT]                     The address above which program text can run.            (27) endcode  %lu  [PT]                     The address below which program text can run.            (28) startstack  %lu  [PT]                     The address of the start (i.e., bottom) of the                     stack.            (29) kstkesp  %lu  [PT]                     The current value of ESP (stack pointer), as found                     in the kernel stack page for the process.            (30) kstkeip  %lu  [PT]                     The current EIP (instruction pointer).            (31) signal  %lu                     The bitmap of pending signals, displayed as a deci‐                     mal number.  Obsolete, because it does not provide                     information on real-time signals; use                     /proc/[pid]/status instead.            (32) blocked  %lu                     The bitmap of blocked signals, displayed as a deci‐                     mal number.  Obsolete, because it does not provide                     information on real-time signals; use                     /proc/[pid]/status instead.            (33) sigignore  %lu                     The bitmap of ignored signals, displayed as a deci‐                     mal number.  Obsolete, because it does not provide                     information on real-time signals; use                     /proc/[pid]/status instead.            (34) sigcatch  %lu                     The bitmap of caught signals, displayed as a decimal                     number.  Obsolete, because it does not provide                     information on real-time signals; use                     /proc/[pid]/status instead.            (35) wchan  %lu  [PT]                     This is the "channel" in which the process is wait‐                     ing.  It is the address of a location in the kernel                     where the process is sleeping.  The corresponding                     symbolic name can be found in /proc/[pid]/wchan.            (36) nswap  %lu                     Number of pages swapped (not maintained).            (37) cnswap  %lu                     Cumulative nswap for child processes (not main‐                     tained).            (38) exit_signal  %d  (since Linux 2.1.22)                     Signal to be sent to parent when we die.            (39) processor  %d  (since Linux 2.2.8)                     CPU number last executed on.            (40) rt_priority  %u  (since Linux 2.5.19)                     Real-time scheduling priority, a number in the range                     1 to 99 for processes scheduled under a real-time                     policy, or 0, for non-real-time processes (see                     sched_setscheduler(2)).            (41) policy  %u  (since Linux 2.5.19)                     Scheduling policy (see sched_setscheduler(2)).                     Decode using the SCHED_* constants in linux/sched.h.                      The format for this field was %lu before Linux                     2.6.22.            (42) delayacct_blkio_ticks  %llu  (since Linux 2.6.18)                     Aggregated block I/O delays, measured in clock ticks                     (centiseconds).            (43) guest_time  %lu  (since Linux 2.6.24)                     Guest time of the process (time spent running a vir‐                     tual CPU for a guest operating system), measured in                     clock ticks (divide by sysconf(_SC_CLK_TCK)).            (44) cguest_time  %ld  (since Linux 2.6.24)                     Guest time of the process's children, measured in                     clock ticks (divide by sysconf(_SC_CLK_TCK)).            (45) start_data  %lu  (since Linux 3.3)  [PT]                     Address above which program initialized and unini‐                     tialized (BSS) data are placed.            (46) end_data  %lu  (since Linux 3.3)  [PT]                     Address below which program initialized and unini‐                     tialized (BSS) data are placed.            (47) start_brk  %lu  (since Linux 3.3)  [PT]                     Address above which program heap can be expanded                     with brk(2).            (48) arg_start  %lu  (since Linux 3.5)  [PT]                     Address above which program command-line arguments                     (argv) are placed.            (49) arg_end  %lu  (since Linux 3.5)  [PT]                     Address below program command-line arguments (argv)                     are placed.            (50) env_start  %lu  (since Linux 3.5)  [PT]                     Address above which program environment is placed.            (51) env_end  %lu  (since Linux 3.5)  [PT]                     Address below which program environment is placed.            (52) exit_code  %d  (since Linux 3.5)  [PT]                     The thread's exit status in the form reported by                     waitpid(2). 

Answer 2

There are enough information on its man page. Try to read it and look for /proc/[pid]/stat in it.

man 5 proc 

In addition to that, you can find its online man page in the following link http://man7.org/linux/man-pages/man5/proc.5.html

Open the URL and search the page for this expression: /proc/[pid]/stat

Hope you will find your answer there! Have a great day!