bash-cc

#! /bin/bash
# e: die if command returns with error, unless
#    command if part of if/where/simmilar
# u: erro out when expanding a undefined variable.
#    use ${1:-} for possible numeric variables
#  o pipefail: a pipeline’s return status is
#              the value of the last (rightmost)
#              command to exit with a non-zero
#              status or 0
set -euo pipefail

# The relative path to the script this variable 
# is expanded in.
echo "${BASH_SOURCE[0]}"

# If/while etc just checks the return code of it's 
# arguemnt. the argument may be a command or 
# multiple &&/|| together, or the test binary 
# called with [ (see bash -c help test)

if false; then
  echo this is false
# Using subshell as file descriptor
elif grep -i PAT <(echo pattern); then
  echo found pattern1
fi

# Redirecting a file (techincally subshell) to
# stdin (echo PATTERN | grep ... is proably smarter)
if grep PAT < <(echo PATTERN); then
  echo found pattern2
else
  echo not found
fi

if false && [ "a" = "a" -a 1 -eq 1 ]; then
  echo false \&\& true
elif [ "a" = "a" -a 1 -eq 1 ] || false; then
  echo true \&\& false
elif (false && true) || true; then
  echo return code of subshell \(false\) or true
else
  echo it\'s false
fi

# Find missing numbers (numbers in first column()
awk '$1!=p+1{print p+1"-"$1-1}{p=$1}'