-f

Output appended data as the file grows.

-o

Write command output to file instead of standard output.

-r

Undump, write back edited login information into the utmp or wtmp files.

-V

Display version information and exit.

-h

Display help text and exit.NOTESutmpdump can be useful in cases of corrupted utmp or wtmp entries. It can dump out utmp/wtmp to an ASCIIfile, which can then be edited to remove bogus entries, and reintegrated using:utmpdump -r < ascii_file > wtmpBut be warned, utmpdump was written for debugging purposes only.File formatsThe only binary version of the utmp(5) is standardised. Textual dumps may become incompatible in future.The version 2.28 was the last one that printed text output using ctime(3) timestamp format. Newer dumps usemillisecond precision ISO-8601 timestamp format in UTC-0 timezone. Conversion from former timestamp formatcan be made to binary, although attempt to do so can lead the timestamps to drift amount of timezone offset.BUGSYou may not use the -r option, as the format for the utmp/wtmp files strongly depends on the input format.This tool was not written for normal use, but for debugging only.AUTHORMichael Krapp