NAME

       acct - process accounting file

SYNOPSIS

       #include <sys/acct.h>

DESCRIPTION

       If    the    kernel    is    built    with   the   process   accounting   option   enabled
       (CONFIG_BSD_PROCESS_ACCT), then calling acct(2) starts process accounting, for example:

           acct("/var/log/pacct");

       When process accounting is enabled, the kernel writes a record to the accounting  file  as
       each  process  on  the  system  terminates.   This  record  contains information about the
       terminated process, and is defined in <sys/acct.h> as follows:

           #define ACCT_COMM 16

           typedef u_int16_t comp_t;

           struct acct {
               char ac_flag;           /* Accounting flags */
               u_int16_t ac_uid;       /* Accounting user ID */
               u_int16_t ac_gid;       /* Accounting group ID */
               u_int16_t ac_tty;       /* Controlling terminal */
               u_int32_t ac_btime;     /* Process creation time
                                          (seconds since the Epoch) */
               comp_t    ac_utime;     /* User CPU time */
               comp_t    ac_stime;     /* System CPU time */
               comp_t    ac_etime;     /* Elapsed time */
               comp_t    ac_mem;       /* Average memory usage (kB) */
               comp_t    ac_io;        /* Characters transferred (unused) */
               comp_t    ac_rw;        /* Blocks read or written (unused) */
               comp_t    ac_minflt;    /* Minor page faults */
               comp_t    ac_majflt;    /* Major page faults */
               comp_t    ac_swaps;     /* Number of swaps (unused) */
               u_int32_t ac_exitcode;  /* Process termination status
                                          (see wait(2)) */
               char      ac_comm[ACCT_COMM+1];
                                       /* Command name (basename of last
                                          executed command; null-terminated) */
               char      ac_pad[X];    /* padding bytes */
           };

           enum {          /* Bits that may be set in ac_flag field */
               AFORK = 0x01,           /* Has executed fork, but no exec */
               ASU   = 0x02,           /* Used superuser privileges */
               ACORE = 0x08,           /* Dumped core */
               AXSIG = 0x10            /* Killed by a signal */
           };

       The comp_t data type is a floating-point value consisting of a 3-bit, base-8 exponent, and
       a  13-bit  mantissa.   A  value,  c,  of this type can be converted to a (long) integer as
       follows:

           v = (c & 0x1fff) << (((c >> 13) & 0x7) * 3);

       The ac_utime, ac_stime, and ac_etime fields measure time in "clock  ticks";  divide  these
       values by sysconf(_SC_CLK_TCK) to convert them to seconds.

   Version 3 accounting file format
       Since kernel 2.6.8, an optional alternative version of the accounting file can be produced
       if the CONFIG_BSD_PROCESS_ACCT_V3 option is set  when  building  the  kernel.   With  this
       option  is  set, the records written to the accounting file contain additional fields, and
       the width of c_uid and ac_gid fields is widened from 16 to  32  bits  (in  line  with  the
       increased  size  of  UID  and  GIDs  in  Linux 2.4 and later).  The records are defined as
       follows:

           struct acct_v3 {
               char      ac_flag;      /* Flags */
               char      ac_version;   /* Always set to ACCT_VERSION (3) */
               u_int16_t ac_tty;       /* Controlling terminal */
               u_int32_t ac_exitcode;  /* Process termination status */
               u_int32_t ac_uid;       /* Real user ID */
               u_int32_t ac_gid;       /* Real group ID */
               u_int32_t ac_pid;       /* Process ID */
               u_int32_t ac_ppid;      /* Parent process ID */
               u_int32_t ac_btime;     /* Process creation time */
               float     ac_etime;     /* Elapsed time */
               comp_t    ac_utime;     /* User CPU time */
               comp_t    ac_stime;     /* System time */
               comp_t    ac_mem;       /* Average memory usage (kB) */
               comp_t    ac_io;        /* Characters transferred (unused) */
               comp_t    ac_rw;        /* Blocks read or written
                                          (unused) */
               comp_t    ac_minflt;    /* Minor page faults */
               comp_t    ac_majflt;    /* Major page faults */
               comp_t    ac_swaps;     /* Number of swaps (unused) */
               char      ac_comm[ACCT_COMM]; /* Command name */
           };

VERSIONS

       The acct_v3 structure is defined in glibc since version 2.6.

CONFORMING TO

       Process accounting originated on BSD.  Although it is present on most systems, it  is  not
       standardized, and the details vary somewhat between systems.

NOTES

       Records in the accounting file are ordered by termination time of the process.

       In  kernels  up  to  and including 2.6.9, a separate accounting record is written for each
       thread created using the NPTL threading library; since Linux 2.6.10, a  single  accounting
       record is written for the entire process on termination of the last thread in the process.

       The  /proc/sys/kernel/acct  file,  described in proc(5), defines settings that control the
       behavior of process accounting when disk space runs low.

SEE ALSO

       lastcomm(1), acct(2), accton(8), sa(8)

COLOPHON

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       project,  information  about  reporting  bugs, and the latest version of this page, can be
       found at https://www.kernel.org/doc/man-pages/.