specplot: 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 Debian possible default full paths are:

/usr/bin/specplot - from package: argyll

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

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