telegram-bot-bash/doc/5_practice.md
Kay Marquardt (Gnadelwartz) c527d175f0 add config examples
2019-04-23 12:17:39 +02:00

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Best Practices

Customize commands.sh only

To ease Updates never change bashbot.sh, instead individual commands should go to commands.sh . Insert your Bot commands in the case ... esac block:

	case "$MESSAGE" in
		'/echo') # my first own command, echo MESSAGE
			send_normal_message "${CHAT[ID]}" "${MESSAGE}"
			;;

		################################################
		# DEFAULT commands start here, do not edit below this!
		'/info')
			bashbot_info "${CHAT[ID]}"
			;;
	esac

Seperate logic from commands

If a command need more than 2-3 lines of code, you should use a function to seperate logic from command. Place your functions in a seperate file, e.g. mycommands.inc.sh and source it from bashbot.sh. Example:

	source "mycommands.inc.sh"

	case "$MESSAGE" in
		'/process') # logic for /process is done in process_message 
			result="$(process_message "$MESSAGE")"
			send_normal_message "${CHAT[ID]}" "$result" 
			;;

		################################################
		# DEFAULT commands start here, do not edit below this!
		'/info')
			bashbot_info "${CHAT[ID]}"
			;;
		'/start')
			send_action "${CHAT[ID]}" "typing"
			bashbot_help "${CHAT[ID]}"
			;;
	esac
#!/bin/bash
# file: mycommands.inc.sh

process_message() {
   local ARGS="${1#/* }"	# remove command 
   local TEXT OUTPUT=""

   # process every word in MESSAGE, avoid globbing
   set -f
   for WORD in $ARGS
   do
	set +f
	# process links 
	if [[ "$WORD" == "https://"* ]]; then
		REPORT="$(dosomething_with_link "$WORD")"
	# no link, add as text
	else
		TEXT="$(echo "${TEXT} $WORD")"
		continue
	fi
	# compose result
	OUTPUT="* ${REPORT} ${WORD} ${TEXT}"
	TEXT=""
   done

   # return result, reset globbing in case we had no ARGS
   set +f
   echo "${OUTPUT}${TEXT}"
}

Test your Bot with shellcheck

Shellcheck is a static linter for shell scripts providing excellent tips and hints for shell coding pittfalls. You can use it online or install it on your system. All bashbot scripts are linted by shellcheck.

Shellcheck examples:

$ shellcheck -x mybotcommands.inc.sh
 
Line 17:
                TEXT="$(echo "${TEXT} $WORD")"
                      ^-- SC2116: Useless echo? Instead of 'cmd $(echo foo)', just use 'cmd foo'.
 

As you can see my mybotcommands.inc.sh contains an useless echo command in 'TEXT=' assigment and can be replaced by TEXT="${TEXT}${WORD}"

$ shellcheck -x examples/notify
OK
$ shellcheck -x examples/question
OK
$ shellcheck -x commands.sh
OK
$ shellcheck -x bashbot.sh

In bashbot.sh line 123:
                text="$(echo "$text" | sed 's/ mynewlinestartshere /\r\n/g')" # hack for linebreaks in startproc scripts
                        ^-- SC2001: See if you can use ${variable//search/replace} instead.


In bashbot.sh line 490:
        CONTACT[USER_ID]="$(sed -n -e '/\["result",'$PROCESS_NUMBER',"message","contact","user_id"\]/  s/.*\][ \t]"\(.*\)"$/\1/p' <"$TMP")"
        ^-- SC2034: CONTACT appears unused. Verify it or export it.

The example show two warnings in bashbots scripts. The first is a hint you may use shell substitions instead of sed, this is fixed and much faster as the "echo | sed" solution. The second warning is about an unused variable, this is true because in our examples CONTACT is not used but assigned in case you want to use it :-)

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