yaz-client: 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/yaz-client - from package: yaz

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

On Debian possible default full paths are:

/usr/bin/yaz-client - from package: yaz

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

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