spline: 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/spline - from package: plotutils

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

On Debian possible default full paths are:

/usr/bin/spline - from package: plotutils

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

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