triangulate: 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/triangulate - 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/triangulate - from package: GMT

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

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