supybot-plugin-doc: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/supybot-plugin-doc - from package: supybot-gribble
/usr/bin/supybot-plugin-doc - from package: supybot

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/supybot-plugin-doc - from package: supybot

You may install the required package with command apt-get install {package}

Error in other languages:
supybot-plugin-doc: bevel nie gevind nie
supybot-plugin-doc: comandă negăsită
supybot-plugin-doc: comando não encontrado
supybot-plugin-doc: commande introuvable
supybot-plugin-doc: command not found
supybot-plugin-doc: käsku ei ole
supybot-plugin-doc: không tìm thấy lệnh
supybot-plugin-doc: komanda nerasta
supybot-plugin-doc: Kommando nicht gefunden.
supybot-plugin-doc: kommandot finns inte
supybot-plugin-doc: komut yok
supybot-plugin-doc: nie znaleziono polecenia
supybot-plugin-doc: níor aimsíodh an t-ordú
supybot-plugin-doc: no se encontró la orden
supybot-plugin-doc: no s'ha trobat l'ordre
supybot-plugin-doc: opdracht niet gevonden
supybot-plugin-doc: parancs nem található
supybot-plugin-doc: perintah tidak ditemukan
supybot-plugin-doc: príkaz nenájdený
supybot-plugin-doc: příkaz nenalezen
supybot-plugin-doc: команда не найдена
supybot-plugin-doc: командата не е открита
supybot-plugin-doc: 命令找不到
supybot-plugin-doc: コマンドが見つかりません