write: 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/write - from package: util-linux-ng

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

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