cic-staff-installer/aux/bash-templater/templater.sh

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2021-11-08 21:39:42 +01:00
#!/bin/bash
# Replaces all {{VAR}} by the $VAR value in a template file and outputs it
# Use with -h to output all variables
if [[ ! -f "$1" ]]; then
echo "Usage: VAR=value $0 template" >&2
exit 1
fi
template="$1"
vars=$(grep -oE '\{\{\s*[A-Za-z0-9_]+\s*\}\}' "$template" | sort | uniq | sed -e 's/^{{//' -e 's/}}$//')
if [[ -z "$vars" ]]; then
echo "Warning: No variable was found in $template, syntax is {{VAR}}" >&2
fi
var_value() {
var="${1}"
eval echo \$"${var}"
}
##
# Escape custom characters in a string
# Example: escape "ab'\c" '\' "'" ===> ab\'\\c
#
function escape_chars() {
local content="${1}"
shift
for char in "$@"; do
content="${content//${char}/\\${char}}"
done
echo "${content}"
}
function echo_var() {
local var="${1}"
local content="${2}"
local escaped="$(escape_chars "${content}" "\\" '"')"
echo "${var}=\"${escaped}\""
}
declare -a replaces
replaces=()
# Reads default values defined as {{VAR=value}} and delete those lines
# There are evaluated, so you can do {{PATH=$HOME}} or {{PATH=`pwd`}}
# You can even reference variables defined in the template before
defaults=$(grep -oE '^\{\{[A-Za-z0-9_]+=.+\}\}$' "${template}" | sed -e 's/^{{//' -e 's/}}$//')
IFS=$'\n'
for default in $defaults; do
var=$(echo "${default}" | grep -oE "^[A-Za-z0-9_]+")
current="$(var_value "${var}")"
# Replace only if var is not set
if [[ -n "$current" ]]; then
eval "$(echo_var "${var}" "${current}")"
else
eval "${default}"
fi
# remove define line
replaces+=("-e")
replaces+=("/^{{${var}=/d")
vars="${vars} ${var}"
done
vars="$(echo "${vars}" | tr " " "\n" | sort | uniq)"
if [[ "$2" = "-h" ]]; then
for var in $vars; do
value="$(var_value "${var}")"
echo_var "${var}" "${value}"
done
exit 0
fi
# Replace all {{VAR}} by $VAR value
for var in $vars; do
value="$(var_value "${var}")"
if [[ -z "$value" ]]; then
echo "Warning: $var is not defined and no default is set, replacing by empty" >&2
fi
# Escape slashes
value="$(escape_chars "${value}" "\\" '/' ' ')";
replaces+=("-e")
replaces+=("s/{{\s*${var}\s*}}/${value}/g")
done
sed "${replaces[@]}" "${template}"