apgdiff: 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/apgdiff - from package: apgdiff

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

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