gif2hdf: 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/gif2hdf - from package: hdf

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

On Debian possible default full paths are:

/usr/bin/gif2hdf - from package: hdf4-tools

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

Error in other languages:
gif2hdf: bevel nie gevind nie
gif2hdf: comandă negăsită
gif2hdf: comando não encontrado
gif2hdf: commande introuvable
gif2hdf: command not found
gif2hdf: käsku ei ole
gif2hdf: không tìm thấy lệnh
gif2hdf: komanda nerasta
gif2hdf: Kommando nicht gefunden.
gif2hdf: kommandot finns inte
gif2hdf: komut yok
gif2hdf: nie znaleziono polecenia
gif2hdf: níor aimsíodh an t-ordú
gif2hdf: no se encontró la orden
gif2hdf: no s'ha trobat l'ordre
gif2hdf: opdracht niet gevonden
gif2hdf: parancs nem található
gif2hdf: perintah tidak ditemukan
gif2hdf: príkaz nenájdený
gif2hdf: příkaz nenalezen
gif2hdf: команда не найдена
gif2hdf: командата не е открита
gif2hdf: 命令找不到
gif2hdf: コマンドが見つかりません