Disk usage

diskusage

#!/bin/bash

#
# This is a script to log (and eventually monitor) diskusage on a filesystem.
# It will write the disk usage to a logfile.
# The logfile will never grow larger than MAX_LINES number of lines.
#
# The script is 'gnu awk' specific. GNU AWK is available on mac (brew) 
# and ubuntu (apt-get) as the package 'gawk'.
#
# To be used together with a cron job and optionally a GNUPLOT.
#

## These vars hold the names of the used files
BASE_NAME="${HOME}/example"
LOG_FILE="${BASE_NAME}.log"
ERR_FILE="${BASE_NAME}.err"
TMP_FILE="${BASE_NAME}.tmp"

# Extract CAPACITY in percentage for the given filesystem
# and append DATETIME and CAPACITY to file
df --output="pcent" ${HOME} | \
    awk 'BEGIN {datetime = strftime("%Y-%m-%dT%H:%M:%S%z", systime());} NR > 1 {print datetime, $1}' \
    >> ${LOG_FILE} 2>>${ERR_FILE}

# If diskusage file does not exist, something went wrong. Better exit.
if [ ! -f "$LOG_FILE" ]; then
    exit 1
fi

#
# Make sure this file doesn't grow larger than MAX_LINES lines.
# Delete oldest entries.
#

# Maximum number of lines the logfile may hold
MAX_LINES=1000

# Number of lines the logfile currently holds
CURRENT_LINES=$(cat ${LOG_FILE} | wc -l)

if [ "$CURRENT_LINES" -gt "$MAX_LINES" ]; then

    # Tail MAX_LINES to tempfile and (force) copy back to original logfile

    tail -n${MAX_LINES} ${LOG_FILE} > ${TMP_FILE}
    cp -f ${TMP_FILE} ${LOG_FILE}

fi

exit 0

example.log

2018-01-01T18:00:00+0100 20%
2018-02-01T18:00:00+0100 25%
2018-03-01T18:00:00+0100 25%
2018-04-01T18:00:00+0100 30%
2018-05-01T18:00:00+0100 50%
2018-06-01T18:00:00+0100 55%
2018-07-01T18:00:00+0100 60%
2018-08-01T18:00:00+0100 60%
2018-09-01T18:00:00+0100 80%
2018-10-01T18:00:00+0100 85%
2018-11-01T18:00:00+0100 90%
2018-12-01T18:00:00+0100 95%

plot.diskusage

#!/usr/local/bin/gnuplot

#
# This script plots a linegraph.
#
# It expects an input as created by the diskusage script.
#
# More specifically, it expects the first column of the logfile to contain
# a date according to the ISO8601 format and the second column to contain
# percentages in the range of 0% - 100%.
#
# Furthermore, it expects gnuplot to be installed at the specified location.
#
# You can run the script by making it executable and running it while
# redirecting the output to a png, e.g.:
#
# ./plot.diskusage > plot.example.log.png
#

# General setup
reset
set terminal png

# Configure general linegraph properties
set title "Disk usage over time"
set key reverse Left outside
set grid
set style data linespoints

# Configure x axis
set xdata time
set timefmt "%Y-%m-%dT%H:%M:%S"
set format x "%Y-%m-%d"
set xlabel "Date"
set xtics rotate by -45

# Configure y axis
set ylabel "Diskusage"
set yrange [0:100]

# Plot capacity (col 2) over time (col 1)
plot "example.log" using 1:2 title "Capacity"

plot.example.log.png