pnmsplit: 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/pnmsplit - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/pnmsplit - from package: netpbm

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

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