acct - process accounting file

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. Version3accountingfileformat Since Linux 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 */ };

glibc 2.6. Process accounting originated on BSD.

acct - process accounting file

Records in the accounting file are ordered by termination time of the process. Up to and including Linux 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.

lastcomm(1), acct(2), accton(8), sa(8) Linux man-pages 6.9.1 2024-05-02 acct(5)

None.

Although it is present on most systems, it is not standardized, and the details vary somewhat between systems.