mgd77list: 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/mgd77list - from package: GMT

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

On Debian possible default full paths are:

/usr/lib/gmt/bin/mgd77list - from package: GMT

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

Error in other languages:
mgd77list: bevel nie gevind nie
mgd77list: comandă negăsită
mgd77list: comando não encontrado
mgd77list: commande introuvable
mgd77list: command not found
mgd77list: käsku ei ole
mgd77list: không tìm thấy lệnh
mgd77list: komanda nerasta
mgd77list: Kommando nicht gefunden.
mgd77list: kommandot finns inte
mgd77list: komut yok
mgd77list: nie znaleziono polecenia
mgd77list: níor aimsíodh an t-ordú
mgd77list: no se encontró la orden
mgd77list: no s'ha trobat l'ordre
mgd77list: opdracht niet gevonden
mgd77list: parancs nem található
mgd77list: perintah tidak ditemukan
mgd77list: príkaz nenájdený
mgd77list: příkaz nenalezen
mgd77list: команда не найдена
mgd77list: командата не е открита
mgd77list: 命令找不到
mgd77list: コマンドが見つかりません