gv: 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/gv - from package: gv

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

On Debian possible default full paths are:

/usr/bin/gv - from package: gv

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

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