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ACCT(5)                    Linux Programmer's Manual                   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  CON-
       FIG_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
       This page is part of release 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2008-06-15                           ACCT(5)