histogram-by-date

#!/bin/sh
set -euf -o pipefail

##
# Histogram by date, on the command line
#
# Credit: Small labs Inc.
# See http://www.smallmeans.com/notes/shell-history/
#
# How it works:
#
#   * grep ...           Select lines that start with YYYYMMDD (optional - or /)
#   * sed ...            Delete everything after the date
#   * sort               Sort, so that similar commands come in groups
#   * uniq -c            Count subsequent items (-c prepends count)
#   * sort -rn           Sort in descending order (reverse)
#   * head -20           Get the 20 most frequent commands
#
#   * awk '!max{max=$1;}{      Everything is nice and in order:
#          r="";               run thru the items, format, pad, print
#          i=s=60*$1/max;
#          while(i-->0){
#            r=r"#";           string concatenation, AWK-style
#          }
#          printf "%15s %5d %s %s",$2,$1,r,"\n";
#        }'
#
# Example:
#
#   cat log | histogram-by-date
#
# Contact: Joel Parker Henderson (joel@joelparkerhenderson.com)
# License: GPL
# Updated: 2015-01-25
##

grep '^ *[0-9][0-9][0-9][0-9][-/]\?[0-9][0-9][-/]\?[0-9][0-9]\b' | sed 's/^ *\([0-9][0-9][0-9][0-9][-/]\?[0-9][0-9][-/]\?[0-9][0-9]\)\b.*/\1/' | histogram