03-15-2019
Quote:
Originally Posted by
Xubuntu56
Why does this until false; do history | head -5; done
result in a stdout infinite loop, yet until false; do history | head -5 > hist5; done
only writes it once to file hist5? Furthermore, I can hear the hard drive working on the 2nd command until I end the process, but the history | head -5 is only written once.
It does not write once. It writes continously without break the
same 5 lines into hist5 file over and over and generates considerable load at your machine. Since every session has its own history this makes no sense to do.
I'm unsure, but I assume .bash_history file is written at logout. If you want to see another sessions history with this, this will not work.
This User Gave Thanks to stomp For This Post:
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LEARN ABOUT DEBIAN
prunehistory
PRUNEHISTORY(8) System Manager's Manual PRUNEHISTORY(8)
NAME
prunehistory - remove file names from Usenet history file
SYNOPSIS
prunehistory [ -f filename ] [ -p ] [ input ]
DESCRIPTION
Prunehistory modifies the history(5) text file to ``remove'' a set of filenames from it. The filenames are removed by overwriting them
with spaces, so that the size and position of any following entries does not change.
Prunehistory reads the named input file, or standard input if no file is given. The input is taken as a set of lines. Blank lines and
lines starting with a number sign (``#'') are ignored. All other lines are should consist of a Message-ID followed by zero or more file-
names.
The Messge-ID is used as the dbz(3) key to get an offset into the text file. If no filenames are mentioned on the input line, then all
filenames in the text are ``removed.'' If any filenames are mentioned, they are converted into the history file notation. If they appear
in the line for the specified Message-ID then they are removed.
Since innd(8) only appends to the text file, prunehistory does not need to have any interaction with it.
OPTIONS
-p Prunehistory will normally complain about lines that do not follow the correct format. If the ``-p'' flag is used, then the program
will silently print any invalid lines on its standard output. (Blank lines and comment lines are also passed through.) This can be
useful when prunehistory is used as a filter for other programs such as reap.
-f The default name of the history file is /var/lib/news/history; to specify a different name, use the ``-f'' flag.
EXAMPLES
It is a good idea to delete purged entries and rebuild the dbz database every so often by using a script like the following:
ctlinnd throttle "Rebuilding history database"
cd /var/lib/news
awk 'NF > 2 {
printf "%s %s %s", $1, $2, $3;
for (i = 4; i <= NF; i++)
printf " %s", $i;
print "
";
}' <history >history.n
if makehistory -r -f history.n ; then
mv history.n history
mv history.n.pag history.pag
mv history.n.dir history.dir
else
echo 'Problem rebuilding history; old file not replaced'
fi
ctlinnd go "Rebuilding history database"
Note that this keeps no record of expired articles.
HISTORY
Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews. This is revision 1.9, dated 1996/10/29.
SEE ALSO
dbz(3), history(5), innd(8).
PRUNEHISTORY(8)