voikkogc: 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/voikkogc - from package: voikko-tools

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

On Debian possible default full paths are:

/usr/bin/voikkogc - from package: libvoikko-dev

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

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