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 account-
       ing, 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

       This  page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2008-06-15								   ACCT(5)