vars.o: 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 Debian possible default full paths are:

/usr/lib/x86_64-linux-gnu/gap/bin/vars.o - from package: gap-dev

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

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