1ACCT(5)                    Linux Programmer's Manual                   ACCT(5)
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NAME

6       acct - process accounting file
7

SYNOPSIS

9       #include <sys/acct.h>
10

DESCRIPTION

12       If the kernel is built with the process accounting option enabled (CON‐
13       FIG_BSD_PROCESS_ACCT), then calling acct(2) starts process  accounting,
14       for example:
15
16           acct("/var/log/pacct");
17
18       When  process  accounting is enabled, the kernel writes a record to the
19       accounting file as each process on the system terminates.  This  record
20       contains  information  about  the terminated process, and is defined in
21       <sys/acct.h> as follows:
22
23           #define ACCT_COMM 16
24
25           typedef u_int16_t comp_t;
26
27           struct acct {
28               char ac_flag;           /* Accounting flags */
29               u_int16_t ac_uid;       /* Accounting user ID */
30               u_int16_t ac_gid;       /* Accounting group ID */
31               u_int16_t ac_tty;       /* Controlling terminal */
32               u_int32_t ac_btime;     /* Process creation time
33                                          (seconds since the Epoch) */
34               comp_t    ac_utime;     /* User CPU time */
35               comp_t    ac_stime;     /* System CPU time */
36               comp_t    ac_etime;     /* Elapsed time */
37               comp_t    ac_mem;       /* Average memory usage (kB) */
38               comp_t    ac_io;        /* Characters transferred (unused) */
39               comp_t    ac_rw;        /* Blocks read or written (unused) */
40               comp_t    ac_minflt;    /* Minor page faults */
41               comp_t    ac_majflt;    /* Major page faults */
42               comp_t    ac_swaps;     /* Number of swaps (unused) */
43               u_int32_t ac_exitcode;  /* Process termination status
44                                          (see wait(2)) */
45               char      ac_comm[ACCT_COMM+1];
46                                       /* Command name (basename of last
47                                          executed command; null-terminated) */
48               char      ac_pad[X];    /* padding bytes */
49           };
50
51           enum {          /* Bits that may be set in ac_flag field */
52               AFORK = 0x01,           /* Has executed fork, but no exec */
53               ASU   = 0x02,           /* Used superuser privileges */
54               ACORE = 0x08,           /* Dumped core */
55               AXSIG = 0x10            /* Killed by a signal */
56           };
57
58       The comp_t data type is a floating-point value consisting of  a  3-bit,
59       base-8  exponent,  and a 13-bit mantissa.  A value, c, of this type can
60       be converted to a (long) integer as follows:
61
62           v = (c & 0x1fff) << (((c >> 13) & 0x7) * 3);
63
64       The ac_utime, ac_stime, and ac_etime  fields  measure  time  in  "clock
65       ticks";  divide these values by sysconf(_SC_CLK_TCK) to convert them to
66       seconds.
67
68   Version 3 accounting file format
69       Since kernel 2.6.8, an optional alternative version of  the  accounting
70       file  can  be  produced if the CONFIG_BSD_PROCESS_ACCT_V3 option is set
71       when building the kernel.  With this option is set, the records written
72       to  the  accounting  file  contain  additional fields, and the width of
73       c_uid and ac_gid fields is widened from 16 to 32 bits (in line with the
74       increased  size  of  UID and GIDs in Linux 2.4 and later).  The records
75       are defined as follows:
76
77           struct acct_v3 {
78               char      ac_flag;      /* Flags */
79               char      ac_version;   /* Always set to ACCT_VERSION (3) */
80               u_int16_t ac_tty;       /* Controlling terminal */
81               u_int32_t ac_exitcode;  /* Process termination status */
82               u_int32_t ac_uid;       /* Real user ID */
83               u_int32_t ac_gid;       /* Real group ID */
84               u_int32_t ac_pid;       /* Process ID */
85               u_int32_t ac_ppid;      /* Parent process ID */
86               u_int32_t ac_btime;     /* Process creation time */
87               float     ac_etime;     /* Elapsed time */
88               comp_t    ac_utime;     /* User CPU time */
89               comp_t    ac_stime;     /* System time */
90               comp_t    ac_mem;       /* Average memory usage (kB) */
91               comp_t    ac_io;        /* Characters transferred (unused) */
92               comp_t    ac_rw;        /* Blocks read or written
93                                          (unused) */
94               comp_t    ac_minflt;    /* Minor page faults */
95               comp_t    ac_majflt;    /* Major page faults */
96               comp_t    ac_swaps;     /* Number of swaps (unused) */
97               char      ac_comm[ACCT_COMM]; /* Command name */
98           };
99

VERSIONS

101       The acct_v3 structure is defined in glibc since version 2.6.
102

CONFORMING TO

104       Process accounting originated on BSD.  Although it is present  on  most
105       systems,  it is not standardized, and the details vary somewhat between
106       systems.
107

NOTES

109       Records in the accounting file are ordered by termination time  of  the
110       process.
111
112       In  kernels  up to and including 2.6.9, a separate accounting record is
113       written for each thread created using the NPTL threading library; since
114       Linux  2.6.10,  a  single  accounting  record is written for the entire
115       process on termination of the last thread in the process.
116
117       The /proc/sys/kernel/acct file, described in proc(5), defines  settings
118       that  control  the  behavior of process accounting when disk space runs
119       low.
120

SEE ALSO

122       lastcomm(1), acct(2), accton(8), sa(8)
123

COLOPHON

125       This page is part of release 4.15 of the Linux  man-pages  project.   A
126       description  of  the project, information about reporting bugs, and the
127       latest    version    of    this    page,    can     be     found     at
128       https://www.kernel.org/doc/man-pages/.
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132Linux                             2017-09-15                           ACCT(5)
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