Random Sample

rsample.sh

#!/bin/bash

############################################################################
# Random Sample - rsample.sh
# 
# A utility to output a sample number of lines from 
# a text file based on a percentage passed in as an
# argument.
#
# Dependencies:
# - shuf (http://man7.org/linux/man-pages/man1/shuf.1.html)
#   - In macOS, shuf is part of core-utils. Install with
#     `brew install coreutils`.
#
# Tested on macOS with zsh.
# 
# Copyright 2020 Eric A. Soto, [email protected]
# 
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the 
# Software is furnished to do so, subject to the following conditions:
# - The above copyright notice and this permission notice shall be 
#   included in all copies or substantial portions of the Software.
# - THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
#   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
#   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
#   IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 
#   CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 
#   TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 
#   SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
############################################################################

# Helpers

# Shows a banner to be used in other error messages.
function showBanner() {
  echo "Random Sample - $0"
}

# Outputs the syntax of the command
function showSyntax() {
  showBanner
  echo "Syntax: $0 [percent] [/path/to/file]"
  echo "  percent - an integer, percent of the total file to output randomly."
  echo "  file    - The full path to the file to sample."
  echo "Output is to stdout. Redirect to save to file."
  echo ""
}

# Used to report that the input file is not present
function missingFile() {
  showBanner
  echo "Missing file: $1"
}

# Let's do this!

# Sanity - we expect two args
if [ $# -lt 2 ]; then
  showSyntax
  exit -1
fi

# Assign incoming arguments
PERCENT=$1
INFILEPATH=$2

# Sanity - is file present?
if [ ! -e $INFILEPATH ]; then
  missingFile $INFILEPATH
  exit -2;
fi

# ASSERT: We have two arguments, and the file exists.

# Figure out how many lines the file has
lineCount=$(wc -l < $INFILEPATH)

# Calc percent of lines (note, this does integer math by default!)
let sampleCount=lineCount*$PERCENT/100

# Output sampleCount
shuf -n $sampleCount $INFILEPATH