wdiff: 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/wdiff - from package: wdiff

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

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