Print log file lines that have not been read
logtail [-t] -flogfile [-ooffsetfile]
logtail reads a specified file (usually a log file) and writes to the standard output that part of it which has not been read by previous runs of logtail. It prints the appropriate number of bytes from the end of logfile, assuming that all changes that are made to it are to add new characters to it.
logfile must be a plain file. A symlink is not allowed.
logtail stores the information about how much of it has already been read in a separate file called offsetfile. offsetfile can be omitted. If omitted, the file named logfile.offset in the same directory which contains logfile is used by default.
If offsetfile is not empty, the inode of logfile is checked. If the inode is changed, logtail simply prints the entire file. If the inode is not changed but logfile is shorter than it was at the last run of logtail, it writes a warning message to the standard output.
logfile to be read after offset
offsetfile stores offset of previous run
test mode - do not change offset in offsetfile
cannot get the size of logfile
logfile does not exist, is not a plain file, or is not readable
cannot write offsetfile