espretto · September 21, 2022 16:02
diff --git a/bash-snippets.sh b/bash-snippets.sh
 #!/bin/bash
 # ------------------------------------------------------------------------------
 # strict mode
 set -euo pipefail; IFS=$'\n\t'

 # ------------------------------------------------------------------------------
 # notes
 # 
 # - `[` represents the command `test`, use `[[` builtin instead.
 # - `-a` and `-o` are deprecated, use `&&` and `||` instead.
 # - `&&` and `||` cannot be used to construct ternary operations, use if-then-fi instead.
 # - paths beginning with a dash may be misinterpreted as arguments.
 #   either terminate the argument list by `--` or prefix relative paths with `./`.
 # - in arithmetic expressions, use `$(( ${array[$key]} ))` syntax when retrieving
 #   array elements to avoid code injection.
 # - mind that redirections are evaluated sequentially from left-to-right:
 #   `command >out.log 2>&1` redirects _stdout_ first, and then _stderr_.
 # - always validate `cd`

 # ------------------------------------------------------------------------------
 # where am i

 # potentially relative script path (even if sourced)
 SCR_PATH="${BASH_SOURCE[0]}"

 # absolute script path
 SCR_PATH=$(readlink -ne "$SCR_PATH")

 # absolute script directory
 SCR_DIR=${SCR_PATH%/*}

 # script filename
 SCR_NAME=${SCR_PATH##*/}

 # script basename without extension(s)
 SCR_BASE=${SCR_NAME%\.*}
 SCR_BASE=${SCR_NAME%%\.*}

 # create temporary directory in TMPDIR (=/tmp)
 TMP_DIR=$(mktemp -d)

 # create file with random portion next to the script
 SESSION=$(mktemp -p "${SCR_DIR}" "session-XXXXXX")

 # setup exit code trap for cleanup
 cleanup () {
  [[ -d "$TMP_DIR" ]] && rm -rf "$TMP_DIR"
 }

 trap cmd 0 1 2 3 6 13 15 # EXIT HUP INT QUIT ABORT PIPE TERM

 # read single line from another command
 random=$(mktemp -u XXXXXX)
 read -r random < <(mktemp -u XXXXXX);

 # ------------------------------------------------------------------------------
 # logging

 log () {
  typeset loglevel="${1^^}"
  # typeset -u loglevel="$1"
  typeset timestamp=$(date +Iseconds)
  # typeset timestamp=$(date +"%FT%T.%3NZ") # ISO_8601 
  printf "[${loglevel}][${timestamp}] $2\n" >&2
 }

 # log file format string
 LOG_FILE=$(date +"./%F_%H-%M-%S.log")

 # rewire stderr to pass through tee (https://stackoverflow.com/a/19279694)
 exec 3>&2
 exec 2> >(tee -a "$LOG_FILE" >&3)

 # simple interprocess communication using named pipe
 LOG_PIPE=$(mktemp -du)
 mkfifo "$LOG_PIPE"
 trap "rm $LOG_PIPE" TERM INT EXIT
 tee -a "$LOG_FILE" < "$LOG_PIPE" >&2 &
 echo hello 2> "$LOG_PIPE"


 # ------------------------------------------------------------------------------
 # variable expansion / string manipulation

 # require variable to be set
 log debug "input=${input:?}"

 # create and set default value is unset
 log debug "input=${input:-default}"

 # replace all occurrences
 ${var//search/replace}

 # replace first occurence
 ${var/search/replace}

 # strip prefix
 ${var#prefix}

 # strip prefix greedily
 ${var##prefix}

 # strip suffix
 ${var%suffix}

 # strip suffix greedily
 ${var%%suffix}

 # uppercase string (alt: typeset -u text)
 ${text^^}

 # lowercase string (alt: typeset -l text)
 ${text,,}

 # trim left
 ${text##+([:space:])}

 # trim right
 ${text%%+([:space:])}

 # substring characters 5,6,7
 ${text:5:3}

 # ------------------------------------------------------------------------------
 # normalize paths

 # fails if any path segment is missing
 ABS_PATH=$(readlink -ne "$filepath")

 # fails if last path segment is missing
 ABS_PATH=$(readlink -nf "$filepath")

 # never fails, prepare for file/dir creation
 ABS_PATH=$(readlink -nm "$filepath")

 # verify required command is available
 command -v git || { log error "missing git"; exit 1 }

 # user interaction
 confirm () {
  read -p "$1 (y/N)? " ask
  [[ "$ask" == [yY] ]]
  return
 }

 # ask user's choice
 confirm "continue" || { log debug "user exit"; exit }

 # quietly unzip to target directory
 unzip -q -d "./target/dir/" "$filepath"

 # ------------------------------------------------------------------------------
 # file interaction

 # read lines from input file
 while IFS= read -r line; do
  # skip empty lines
  [[ -n "$line" ]] || continue
  echo "$line"
 done < $(<input.txt)

 # read lines from another command avoiding subshell+buffering using FIFO
 while IFS= read -r line; do
  echo "$line"
 done < <(find . -type f -name "*.log")

 # ------------------------------------------------------------------------------
 # split string
 array=()
 while read -rd "$delimiter" substring; do
    array+=("$substring")
 done < <(printf '%s%s' "$input" "$delim")

 # IFS is a field terminator, not a separator
 IFS=, read -ra array <<< "a,b,c,"

 join () {
  typeset IFS="${1}"; shift;
  printf "${*}";
 }

 # join path segments
 filepath=$(join '/' path to file)

 # download file
 curl -o "$filepath" "$url"

 # verify md5 checksum
 if ! curl "${url}.md5" | md5sum -c -; then
  log error "checksum mismatch. corrupted download suspected at ${filepath}"
  exit 1
 fi

 # ------------------------------------------------------------------------------
 # read and render .properties config files

 read_properties () {
  typeset -n props="$1"
  while IFS== read -r key value; do
    props["$key"]="$value"
  done
 }

 render_template () {
  typeset -n props="$1"
  typeset pattern='\{\{([^\}[:space:]]+)\}\}'
  typeset line key value
  
  while IFS= read -r line; do
    while [[ "$line" =~ $pattern ]]; do
      key="${BASH_REMATCH[1]}"
      value="${props[$key]}"
      
      if [[ -n "$value" ]]; then
        line="${line/$BASH_REMATCH/$value}"
      else
        break
      fi
    done
    
    echo "$line"
  done
 }

 declare -A PROPS
 read_properties PROPS < app.properties
 render_template PROPS < template.conf > rendered.conf

 # ------------------------------------------------------------------------------
 # remote script execution

 run_remote () {
  typeset args script

  script=$1; shift

  # generate eval-safe quoted version of current argument list
  printf -v args '%q ' "$@"

  # pass that through on the command line to bash -s
  # note that $args is parsed remotely by /bin/sh, not by bash!
  ssh user@remote-addr "bash -s -- $args" < "$script"
 }

 # ------------------------------------------------------------------------------
 # handling jar-files

 unzip -d "$tmpdir" "$jarfile" "$extractpath"
 jar -uvf "$jarfile" "$tmpdir/$extractpath"
 rm -rf "$tmpdir"
	#!/bin/bash
	# ------------------------------------------------------------------------------
	# strict mode
	set -euo pipefail; IFS=$'\n\t'

	# ------------------------------------------------------------------------------
	# notes
	#
	# - `[` represents the command `test`, use `[[` builtin instead.
	# - `-a` and `-o` are deprecated, use `&&` and `\|\|` instead.
	# - `&&` and `\|\|` cannot be used to construct ternary operations, use if-then-fi instead.
	# - paths beginning with a dash may be misinterpreted as arguments.
	# either terminate the argument list by `--` or prefix relative paths with `./`.
	# - in arithmetic expressions, use `$(( ${array[$key]} ))` syntax when retrieving
	# array elements to avoid code injection.
	# - mind that redirections are evaluated sequentially from left-to-right:
	# `command >out.log 2>&1` redirects _stdout_ first, and then _stderr_.
	# - always validate `cd`

	# ------------------------------------------------------------------------------
	# where am i

	# potentially relative script path (even if sourced)
	SCR_PATH="${BASH_SOURCE[0]}"

	# absolute script path
	SCR_PATH=$(readlink -ne "$SCR_PATH")

	# absolute script directory
	SCR_DIR=${SCR_PATH%/*}

	# script filename
	SCR_NAME=${SCR_PATH##*/}

	# script basename without extension(s)
	SCR_BASE=${SCR_NAME%\.*}
	SCR_BASE=${SCR_NAME%%\.*}

	# create temporary directory in TMPDIR (=/tmp)
	TMP_DIR=$(mktemp -d)

	# create file with random portion next to the script
	SESSION=$(mktemp -p "${SCR_DIR}" "session-XXXXXX")

	# setup exit code trap for cleanup
	cleanup () {
	[[ -d "$TMP_DIR" ]] && rm -rf "$TMP_DIR"
	}

	trap cmd 0 1 2 3 6 13 15 # EXIT HUP INT QUIT ABORT PIPE TERM

	# read single line from another command
	random=$(mktemp -u XXXXXX)
	read -r random < <(mktemp -u XXXXXX);

	# ------------------------------------------------------------------------------
	# logging

	log () {
	typeset loglevel="${1^^}"
	# typeset -u loglevel="$1"
	typeset timestamp=$(date +Iseconds)
	# typeset timestamp=$(date +"%FT%T.%3NZ") # ISO_8601
	printf "[${loglevel}][${timestamp}] $2\n" >&2
	}

	# log file format string
	LOG_FILE=$(date +"./%F_%H-%M-%S.log")

	# rewire stderr to pass through tee (https://stackoverflow.com/a/19279694)
	exec 3>&2
	exec 2> >(tee -a "$LOG_FILE" >&3)

	# simple interprocess communication using named pipe
	LOG_PIPE=$(mktemp -du)
	mkfifo "$LOG_PIPE"
	trap "rm $LOG_PIPE" TERM INT EXIT
	tee -a "$LOG_FILE" < "$LOG_PIPE" >&2 &
	echo hello 2> "$LOG_PIPE"


	# ------------------------------------------------------------------------------
	# variable expansion / string manipulation

	# require variable to be set
	log debug "input=${input:?}"

	# create and set default value is unset
	log debug "input=${input:-default}"

	# replace all occurrences
	${var//search/replace}

	# replace first occurence
	${var/search/replace}

	# strip prefix
	${var#prefix}

	# strip prefix greedily
	${var##prefix}

	# strip suffix
	${var%suffix}

	# strip suffix greedily
	${var%%suffix}

	# uppercase string (alt: typeset -u text)
	${text^^}

	# lowercase string (alt: typeset -l text)
	${text,,}

	# trim left
	${text##+([:space:])}

	# trim right
	${text%%+([:space:])}

	# substring characters 5,6,7
	${text:5:3}

	# ------------------------------------------------------------------------------
	# normalize paths

	# fails if any path segment is missing
	ABS_PATH=$(readlink -ne "$filepath")

	# fails if last path segment is missing
	ABS_PATH=$(readlink -nf "$filepath")

	# never fails, prepare for file/dir creation
	ABS_PATH=$(readlink -nm "$filepath")

	# verify required command is available
	command -v git \|\| { log error "missing git"; exit 1 }

	# user interaction
	confirm () {
	read -p "$1 (y/N)? " ask
	[[ "$ask" == [yY] ]]
	return
	}

	# ask user's choice
	confirm "continue" \|\| { log debug "user exit"; exit }

	# quietly unzip to target directory
	unzip -q -d "./target/dir/" "$filepath"

	# ------------------------------------------------------------------------------
	# file interaction

	# read lines from input file
	while IFS= read -r line; do
	# skip empty lines
	[[ -n "$line" ]] \|\| continue
	echo "$line"
	done < $(<input.txt)

	# read lines from another command avoiding subshell+buffering using FIFO
	while IFS= read -r line; do
	echo "$line"
	done < <(find . -type f -name "*.log")

	# ------------------------------------------------------------------------------
	# split string
	array=()
	while read -rd "$delimiter" substring; do
	array+=("$substring")
	done < <(printf '%s%s' "$input" "$delim")

	# IFS is a field terminator, not a separator
	IFS=, read -ra array <<< "a,b,c,"

	join () {
	typeset IFS="${1}"; shift;
	printf "${*}";
	}

	# join path segments
	filepath=$(join '/' path to file)

	# download file
	curl -o "$filepath" "$url"

	# verify md5 checksum
	if ! curl "${url}.md5" \| md5sum -c -; then
	log error "checksum mismatch. corrupted download suspected at ${filepath}"
	exit 1
	fi

	# ------------------------------------------------------------------------------
	# read and render .properties config files

	read_properties () {
	typeset -n props="$1"
	while IFS== read -r key value; do
	props["$key"]="$value"
	done
	}

	render_template () {
	typeset -n props="$1"
	typeset pattern='\{\{([^\}[:space:]]+)\}\}'
	typeset line key value

	while IFS= read -r line; do
	while [[ "$line" =~ $pattern ]]; do
	key="${BASH_REMATCH[1]}"
	value="${props[$key]}"

	if [[ -n "$value" ]]; then
	line="${line/$BASH_REMATCH/$value}"
	else
	break
	fi
	done

	echo "$line"
	done
	}

	declare -A PROPS
	read_properties PROPS < app.properties
	render_template PROPS < template.conf > rendered.conf

	# ------------------------------------------------------------------------------
	# remote script execution

	run_remote () {
	typeset args script

	script=$1; shift

	# generate eval-safe quoted version of current argument list
	printf -v args '%q ' "$@"

	# pass that through on the command line to bash -s
	# note that $args is parsed remotely by /bin/sh, not by bash!
	ssh user@remote-addr "bash -s -- $args" < "$script"
	}

	# ------------------------------------------------------------------------------
	# handling jar-files

	unzip -d "$tmpdir" "$jarfile" "$extractpath"
	jar -uvf "$jarfile" "$tmpdir/$extractpath"
	rm -rf "$tmpdir"