whisper-resize: 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/whisper-resize - from package: python-whisper

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

On Debian possible default full paths are:

/usr/bin/whisper-resize - from package: python-whisper

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

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