[pacman-dev] [PATCH 1/1] scripts/library: add config_parser.sh

[Dave Reisner]

On Fri, Sep 30, 2011 at 07:37:48PM +0800, lolilolicon wrote:
> config_parser.sh provides functions to support parsing simple config
> files, pacman.conf in particular.  Our scripts should never use a
> simple eval to get config values such as DBPath.
> 
> conf_key_val() is modified from pacman-key's get_from() function. Please
> note conf_key_val() and conf_key_set() both read config file from stdin,
> instead of $1.

I don't see the advantage of doing it this way. If/when we add a
function like conf_keyval_set() (which actually updates a file) we'll
have to ignore this convention and pass the filename, for obvious
reasons.

At the risk of painting my shed green, I dislike your naming convention,
particularly conf_key_set, which doesn't set anything at all. I would
have thought that something such as the following would be appropriate:

# accessors
conf_key_isset() # determines existance of a key w/o an associated value.
conf_keyval_get() # gets the value of a key.

# mutators
conf_key_set() # sets a key without a value, as long as it doesn't exist.
conf_keyval_set() # sets a key with a value, as long as it doesn't exist.

And of course, accessors return 0/1 to indicate existance, mutators
return 0/1 to indicate write success/failure.

d

> Signed-off-by: lolilolicon <lolilolicon at gmail.com>
> ---
>  scripts/library/README           |    3 ++
>  scripts/library/config_parser.sh |   56 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 59 insertions(+), 0 deletions(-)
>  create mode 100644 scripts/library/config_parser.sh
> 
> diff --git a/scripts/library/README b/scripts/library/README
> index 1e9c962..4fb70dd 100644
> --- a/scripts/library/README
> +++ b/scripts/library/README
> @@ -1,6 +1,9 @@
>  This folder contains code snippets that can be reused by multiple
>  scripts.  A brief description of each file follows.
>  
> +config_parser.sh:
> +Parses simple config files such as pacman.conf.
> +
>  output_format.sh:
>  Provides basic output formatting functions with levels 'msg', 'msg2',
>  'warning' and 'error'.  The 'msg' amd 'msg2' functions print to stdout
> diff --git a/scripts/library/config_parser.sh b/scripts/library/config_parser.sh
> new file mode 100644
> index 0000000..1d125eb
> --- /dev/null
> +++ b/scripts/library/config_parser.sh
> @@ -0,0 +1,56 @@
> +shopt -s extglob
> +
> +# Parse value of a non-repeating key from a config file.
> +#
> +# stdin: config file
> +# $1: key - shall not contain '=', or start/end with whitespaces
> +# $2: default value if not defined in config file [optional]
> +# return:
> +#   0 - print value of key
> +#   1 - print nothing
> +conf_key_val() {
> +	local key val
> +	while IFS='=' read -r key val; do
> +		# strip whitespaces
> +		key=${key##*([[:space:]])}
> +		key=${key%%*([[:space:]])}
> +		val=${val##*([[:space:]])}
> +		val=${val%%*([[:space:]])}

read is the opportune thing to use here -- it's faster (which surprises
me) and more concise.

  read -r key <<< "$key"
  read -r val <<< "$val"

> +		# ignore comments and invalid lines
> +		[[ ${key:0:1} == '#' || -z $key || -z $val ]] && continue
> +		# return success as soon as a value is found
> +		if [[ $key == "$1" ]]; then
> +			printf '%s' "$val"
> +			return 0
> +		fi
> +	done
> +	# fallback to default value if specified
> +	if [[ -n $2 ]]; then
> +		printf '%s' "$2"
> +		return 0
> +	fi
> +	return 1
> +}
> +
> +# Check whether an on/off key is set (on) in a config file.
> +#
> +#	stdin: config file
> +# $1: key - shall not contain '=', or start/end with whitespaces
> +# return:
> +#   0 - key is set
> +#   1 - key is not set
> +conf_key_set() {
> +	local key
> +	while read -r key; do
> +		# strip whitespaces, ignore comments
> +		key=${key##*([[:space:]])}
> +		key=${key%%*([[:space:]])}
> +		# ignore comments and invalid lines
> +		[[ ${key:0:1} == '#' || -z $key ]] && continue
> +		# return success as soon as the key is found
> +		if [[ $key == "$1" ]]; then
> +			return 0
> +		fi
> +	done
> +	return 1
> +}
> -- 
> 1.7.6.4
> 
>