Python implementation of users command in coreutils for GNU/Linux. source code
This script will read /var/run/utmp file and extract the struct utmp from it.
This code does simillar to users command will do.
This project is just a fun project for learning purposes, it's just reading the bytes from utmp files,
Extract data that logged into that file, print it.
man utmp
"""
CONFORMING TO
POSIX.1 does not specify a utmp structure, but rather one named utmpx,
with specifications for the fields ut_type, ut_pid, ut_line, ut_id,
ut_user, and ut_tv. POSIX.1 does not specify the lengths of the ut_line
and ut_user fields.
Linux defines the utmpx structure to be the same as the utmp structure.
**Comparison with historical systems**
Linux utmp entries conform neither to v7/BSD nor to System V; they are a
mix of the two.
v7/BSD has fewer fields; most importantly it lacks ut_type, which causes
native v7/BSD-like programs to display (for example) dead or login en‐
tries. Further, there is no configuration file which allocates slots to
sessions. BSD does so because it lacks ut_id fields.
In Linux (as in System V), the ut_id field of a record will never change
once it has been set, which reserves that slot without needing a configu‐
ration file. Clearing ut_id may result in race conditions leading to
corrupted utmp entries and potential security holes. Clearing the above‐
mentioned fields by filling them with null bytes is not required by Sys‐
tem V semantics, but makes it possible to run many programs which assume
BSD semantics and which do not modify utmp. Linux uses the BSD conven‐
tions for line contents, as documented above.
System V has no ut_host or ut_addr_v6 fields.
"""
"""
The file is a sequence of utmp structures, declared as follows in <utmp.h> (note that this is only one of several definitions around; details depend on the version of libc):
/* Values for ut_type field, below */
#define EMPTY 0 /* Record does not contain valid info
(formerly known as UT_UNKNOWN on Linux) */
#define RUN_LVL 1 /* Change in system run-level (see
init(1)) */
#define BOOT_TIME 2 /* Time of system boot (in ut_tv) */
#define NEW_TIME 3 /* Time after system clock change
(in ut_tv) */
#define OLD_TIME 4 /* Time before system clock change
(in ut_tv) */
#define INIT_PROCESS 5 /* Process spawned by init(1) */
#define LOGIN_PROCESS 6 /* Session leader process for user login */
#define USER_PROCESS 7 /* Normal process */
#define DEAD_PROCESS 8 /* Terminated process */
#define ACCOUNTING 9 /* Not implemented */
#define UT_LINESIZE 32
#define UT_NAMESIZE 32
#define UT_HOSTSIZE 256
struct exit_status { /* Type for ut_exit, below */
short e_termination; /* Process termination status */
short e_exit; /* Process exit status */
};
struct utmp {
short ut_type; /* Type of record */
pid_t ut_pid; /* PID of login process */
char ut_line[UT_LINESIZE]; /* Device name of tty - "/dev/" */
char ut_id[4]; /* Terminal name suffix,
or inittab(5) ID */
char ut_user[UT_NAMESIZE]; /* Username */
char ut_host[UT_HOSTSIZE]; /* Hostname for remote login, or
kernel version for run-level
messages */
struct exit_status ut_exit; /* Exit status of a process
marked as DEAD_PROCESS; not
used by Linux init(1) */
/* The ut_session and ut_tv fields must be the same size when
compiled 32- and 64-bit. This allows data files and shared
memory to be shared between 32- and 64-bit applications. */
#if __WORDSIZE == 64 && defined __WORDSIZE_COMPAT32
int32_t ut_session; /* Session ID (getsid(2)),
used for windowing */
struct {
int32_t tv_sec; /* Seconds */
int32_t tv_usec; /* Microseconds */
} ut_tv; /* Time entry was made */
#else
long ut_session; /* Session ID */
struct timeval ut_tv; /* Time entry was made */
#endif
int32_t ut_addr_v6[4]; /* Internet address of remote
host; IPv4 address uses
just ut_addr_v6[0] */
char __unused[20]; /* Reserved for future use */
};
"""
clone the script from github
git clone https://github.com/parsariyahi/utmp_reader.git
run below command for help
python src/pusers.py --help
NOTE: This script is reading utmpx format that apears in utmp.h. |
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WARNING: for testing purposses, the script is just reading the utmp file from this path "./utmp". |
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WARNING: This script only tested on ubuntu 5.15.0-101-generic x86_64 GNU/Linux |
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