config.h: 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/config.h - from package: gap-dev

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

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