gwenview: 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/gwenview - from package: kdegraphics

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

On Debian possible default full paths are:

/usr/bin/gwenview - from package: gwenview

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

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