vcddiff: 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/vcddiff - from package: gplcver

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

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