coqtop.opt: 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/bin/coqtop.opt - from package: coq

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

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