ftlint: 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/ftlint - from package: freetype-demos

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

On Debian possible default full paths are:

/usr/bin/ftlint - from package: freetype2-demos

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

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