asview: 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/asview - from package: libAfterImage-devel

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

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