问在Linux中，如何在不扫描整个文件的情况下显示过去5分钟内添加的文件内容？

EN

#!/usr/bin/env bash

file=$1; shift                    # first input: filename
grep_opts=( "$@" )                # remaining inputs: grep options

dir=$(dirname -- "$file")         # extract directory name to use for offset storage
basename=${file##*/}              # pick up file name w/o directory
size_file="$dir/.$basename.size"  # generate filename to use to store offset

if [[ -s $size_file ]]; then      # ...if we already have a file with an offset...
  old_size=$(<"$size_file")       # ...read it from that file
else
  old_size=0                      # ...otherwise start at the front.
fi

new_size=$(stat --format=%s -- "$file") || exit  # Figure out current size

if (( new_size < old_size )); then
  old_size=0                          # file was truncated, so we can't trust old_size
elif (( new_size == old_size )); then
  exit 0                              # no new contents, so no point in trying to search
fi

# read starting at old_size and grep only that content
dd iflag=skip_bytes skip="$old_size" if="$file" | grep "${grep_opts[@]}"; grep_retval=$?

# if the read failed, don't store an updated offset
(( ${PIPESTATUS[0]} != 0 )) && exit 1

# create a new tempfile to store offset in
tempfile=$(mktemp -- "${size_file}.XXXXXX") || exit

# write to that temporary file...
printf '%s\n' "$new_size" > "$tempfile" || { rm -f "$tempfile"; exit 1; }

# ...and if that write succeeded, overwrite the last place where we serialized output.
mv -- "$tempfile" "$new_size" || exit

exit "$grep_retval"

#!/usr/bin/env bash

file=$1; shift

start_date=$(date -d 'now - 5 minutes' '+%y%m%d %H:%M:%S')
byte_offset=$(bsearch --byte-offset "$file" "$start_date")

dd iflag=skip_bytes skip="$byte_offset" if="$file" | grep "$@"

DB_FILE="FULL_PATH_TO_YOUR_DB_FILE"

current_db_size=$(du -b "$DB_FILE" | cut -f 1)
if [[ ! -a SOME_PATH_OF_YOUR_CHOICE/last_size_db_file ]] ; then
    tail --bytes $current_db_size $DB_FILE > SOME_PATH_OF_YOUR_CHOICE/log-file_$(date +%Y-%m-%d_%H-%M-%S)
else
    if [[ $(cat last_size_db_file) -gt $current_db_size ]] ; then
        previously_readed_bytes=0
    else
        previously_readed_bytes=$(cat last_size_db_file)
    fi
    new_bytes=$(($current_db_size - $previously_readed_bytes))
    tail --bytes $new_bytes $DB_FILE > SOME_PATH_OF_YOUR_CHOICE/log-file_$(date +%Y-%m-%d_%H-%M-%S)
fi
printf $current_db_size > SOME_PATH_OF_YOUR_CHOICE/last_size_db_file

*/5 * * * * PATH_TO_YOUR_SCRIPT

#!/bin/bash
#
# dummy logfile writer
#
while true
do
  s=$(( $(date +%s) % 3600))
  echo $s server msg
  sleep 3
done >> seconds.log

#!/bin/bash
#
# consume a logfile as written so far. Then, collect every new line
# and show it in an interval of $interval
#
interval=9 # 9 seconds
#
printf -v secnow '%(%s)T' -1 
start=$(( secnow % (3600*24*365) ))
declare -a arr
init=false
while true
do
  read line
  printf -v secnow '%(%s)T' -1 
  now=$(( secnow % (3600*24*365) ))

  # consume every line created in the past
  if (( ! init ))
  then
    # assume reading a line might not take longer than a second (rounded to whole seconds)
    while (( ${#line} > 0 && (now - start) < 2 ))
    do
      read line
      start=$now
      echo -n "." # for debugging purpose, remove  
      printf -v secnow '%(%s)T' -1 
      now=$(( secnow % (3600*24*365) ))
    done
    init=1
    echo "init=$init" # for debugging purpose, remove 
  # collect new lines, display them every $interval seconds
  else
    if ((${#line} > 0 ))
    then
      echo -n "-" # for debugging purpose, remove 
      arr+=("read: $line \n")
    fi
    if (( (now - start) > interval ))
    then
      echo -e "${arr[@]]}"
      arr=()
      start=$now
    fi
  fi
  sleep .1
done < seconds.log

./read-seconds.sh 
.......................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................init=1
---read: 1688 server msg 
 read: 1691 server msg 
 read: 1694 server msg 

---read: 1697 server msg 
 read: 1700 server msg 
 read: 1703 server msg 

----read: 1706 server msg 
 read: 1709 server msg 
 read: 1712 server msg 
 read: 1715 server msg 

^C