Bash – History with bash file

bashcommand history

I'm running a bash file to obtain data on what system processes are running (i.e netstat, syslog, arp etc). All's going well except for the history.
I'm trying to save the history to a text file with

cp ~/. bash_history $path/filename.txt

Unfortunately this doesn't give me the complete history. If manually input the command

history > /media/root/usb/filename

I get a completely different result.
My aim is to automate the whole process under the one bash file, is there a way of doing this. Also i'd ideally like the date and time with the history.

Best Answer

As @Jesse_b commented, .bash_history contains the history of all your previous shell sessions except the current one, which can be examined via the historycommand. So you'll have first to flush the current history via

history -a

and then you can copy it to another file:

cp ~/.bash_history $path/filename.txt

To prepend each history entry with a timestamp, set the $HISTTIMEFORMAT variable, e.g.

HISTTIMEFORMAT="%F %T: "

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You could do something like:

fixhist() {
   local cmd histnum
   cmd=$(HISTTIMEFORMAT=/ history 1)
   histnum=$((${cmd%%[*/]*}))
   cmd=${cmd#*/} # remove the histnum
   case $cmd in
     (rm\ *|mv\ *|...)
       history -d "$histnum" # delete
       history -s "#$cmd"    # add back with a #
   esac
}
PROMPT_COMMAND=fixhist

The idea being that before each prompt, we check the last history entry (history 1) and if it's one of the dangerous ones, we delete it (history -d) and add it back with a # with history -s.

(obviously, you need to remove your HISTIGNORE setting).

An unwanted side effect of that though is that it alters the history time of those rm, mv... commands.

To fix that, an alternative could be:

fixhist() {
   local cmd time histnum
   cmd=$(HISTTIMEFORMAT='<%s>' history 1)
   histnum=$((${cmd%%[<*]*}))
   time=${cmd%%>*}
   time=${time#*<}
   cmd=${cmd#*>}
   case $cmd in
     (rm\ *|mv\ *|...)
       history -d "$histnum" # delete
       HISTFILE=/dev/stdin history -r <<EOF
#$time
#$cmd
EOF
   esac
}
PROMPT_COMMAND=fixhist

This time, we record the time of the last history, and to add back the history line, we use history -r from a temporary file (the here document) that includes the timestamp.

You'd want the fixhist to be performed before your history -a; history -c; history -r. Unfortunately, the current version of bash has a bug in that history -a doesn't save that extra line that we've added. A work around is to write it instead:

fixhist() {
   local cmd time histnum
   cmd=$(HISTTIMEFORMAT='<%s>' history 1)
   histnum=$((${cmd%%[<*]*}))
   time=${cmd%%>*}
   time=${time#*<}
   cmd=${cmd#*>}
   case $cmd in
     (rm\ *|mv\ *|...)
       history -d "$histnum" # delete
       history -a
       [ -f "$HISTFILE" ] && printf '#%s\n' "$time" "$cmd" >> "$HISTFILE";;
     (*)
       history -a
   esac
   history -c
   history -r
}
PROMPT_COMMAND=fixhist

That is to append the commented command to the HISTFILE ourselves instead of letting history -a do it.

Best Answer

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