ACCT(5) BSD Programmer's Manual ACCT(5)NAMEacct - execution accounting file
SYNOPSIS
#include <sys/types.h>
#include <sys/acct.h>
DESCRIPTION
The kernel maintains the following acct information structure for all
processes. If a process terminates, and accounting is enabled, the kernel
calls the acct(2) function call to prepare and append the record to the
accounting file.
/*
* 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
If a terminated process was created by an execve(2), the name of the ex-
ecuted file (at most ten characters of it) is saved in the field ac_comm
and its status is saved by setting one of more of the following flags in
ac_flag: AFORK, ASU, ACOMPAT, ACORE and ASIG.
The unusual coding of the comp_t fields gives a large range (more than 8
years) in a small space (16 bits), at a small cost in accuracy. To con-
vert these fields, use the formula:
u = (v & 0x1fff) << (3 * (v >> 13))
(where v is the comp_t value and u is the time in units of AHZ). The
largest possible value is 8191 * 8^7 or 17,177,772,032 units, which is
about eight and a half years. Note that the numbers remain exact through
8191 units (just under 128 seconds), after which the low three bits of
the value are dropped, so values that represent between 128 and 1023.875
seconds are only accurate to the nearest 8/64 or 1/8th of a second. An-
other three bits disappear for each new power of 8, so values between
1024 and 8191 seconds are only accurate to the second, and so forth.
SEE ALSOlastcomm(1), acct(2), execve(2), sa(8)HISTORY
An acct file format appeared in Version 7 AT&T UNIX.
BSDI BSD/OS February 12, 1998 2