espdiff: 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/espdiff - from package: patchutils

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

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