acct(5)

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

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