gcal2txt: 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/gcal2txt - from package: gcal

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

Error in other languages:
gcal2txt: bevel nie gevind nie
gcal2txt: comandă negăsită
gcal2txt: comando não encontrado
gcal2txt: commande introuvable
gcal2txt: command not found
gcal2txt: käsku ei ole
gcal2txt: không tìm thấy lệnh
gcal2txt: komanda nerasta
gcal2txt: Kommando nicht gefunden.
gcal2txt: kommandot finns inte
gcal2txt: komut yok
gcal2txt: nie znaleziono polecenia
gcal2txt: níor aimsíodh an t-ordú
gcal2txt: no se encontró la orden
gcal2txt: no s'ha trobat l'ordre
gcal2txt: opdracht niet gevonden
gcal2txt: parancs nem található
gcal2txt: perintah tidak ditemukan
gcal2txt: príkaz nenájdený
gcal2txt: příkaz nenalezen
gcal2txt: команда не найдена
gcal2txt: командата не е открита
gcal2txt: 命令找不到
gcal2txt: コマンドが見つかりません