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.\"     @(#)acct.5	8.1 (Berkeley) 6/5/93
.\"
.Dd November 15, 2021
.Dt ACCT 5
.Os
.Sh NAME
.Nm acct
.Nd execution accounting file
.Sh SYNOPSIS
.In sys/acct.h
.Sh DESCRIPTION
The kernel maintains the following
.Fa acct
information structure for all
processes. If a process terminates, and accounting is enabled,
the kernel calls the
.Xr acct 2
function call to prepare and append the record
to the accounting file.
.Bd -literal
/*
 * Accounting structures; these use a comp_t type which is a 3 bits base 8
 * exponent, 13 bit fraction ``floating point'' number.  Units are 1/AHZ
 * seconds.
 */
typedef u_short comp_t;

struct acct {
	char	ac_comm[10];	/* name of command */
	comp_t	ac_utime;	/* user time */
	comp_t	ac_stime;	/* system time */
	comp_t	ac_etime;	/* elapsed time */
	time_t	ac_btime;	/* starting time */
	uid_t	ac_uid;		/* user id */
	gid_t	ac_gid;		/* group id */
	short	ac_mem;		/* memory usage average */
	comp_t	ac_io;		/* count of IO blocks */
	dev_t	ac_tty;		/* controlling tty */
#define	AFORK	0x01		/* forked but not execed */
#define	ASU	0x02		/* used super-user permissions */
#define	ACOMPAT	0x04		/* used compatibility mode */
#define	ACORE	0x08		/* dumped core */
#define	AXSIG	0x10		/* killed by a signal */
	char	ac_flag;	/* accounting flags */
};

/*
 * 1/AHZ is the granularity of the data encoded in the comp_t fields.
 * This is not necessarily equal to hz.
 */
#define	AHZ	64

#ifdef KERNEL
struct vnode	*acctp;
#endif
.Ed
.Pp
If a terminated process was created by an
.Xr execve 2 ,
the name of the executed file (at most ten characters of it)
is saved in the field
.Fa ac_comm
and its status is saved by setting one of more of the following flags in
.Fa ac_flag :
.Dv AFORK ,
.Dv ACORE ,
and
.Dv AXSIG .
.Pp
The
.Dv ASU
flag is not recorded anymore because with the switch to
.Xr kauth 9 ,
the superuser model is optional and passing the affected process to every
authorization call in order to record
.Dv ASU
in
.Fa p_acflag ,
would require many source changes and would not reflect reality because
the authorization decision might not have been done based on the 
.Xr secmodel_suser 9 
model.
.Pp
The
.Dv ACOMPAT
flag was never recorded in
.Nx ;
we could consider setting when the a process is running under emulation,
but this is not currently done.
.Pp
Both the
.Dv ASU
and the
.Dv ACOMPAT
flags are retained for source compatibility.
.Sh SEE ALSO
.Xr lastcomm 1 ,
.Xr acct 2 ,
.Xr execve 2 ,
.Xr accton 8 ,
.Xr sa 8
.Sh HISTORY
A
.Nm
file format appeared in
.At v7 .