gpsim: 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/gpsim - from package: gpsim

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

On Debian possible default full paths are:

/usr/bin/gpsim - from package: gpsim

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

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