hipstopgm: 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/hipstopgm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/hipstopgm - from package: netpbm

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

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