units_cur: command not found

Have You tried accessing the binary with the full path?

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/units_cur - from package: units

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