giffiltr: 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/giffiltr - from package: giflib-utils

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

On Debian possible default full paths are:

/usr/bin/giffiltr - from package: giflib-tools

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

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