sift: 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/sift - from package: python-guiqwt

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

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