linguist: 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/lib64/qt-3.3/bin/linguist - from package: qt3-devel
/usr/lib/qt-3.3/bin/linguist - from package: qt3-devel
/usr/lib64/qt5/bin/linguist - from package: qt5-linguist
/usr/lib64/qt4/bin/linguist - from package: qt-devel
/usr/lib/qt4/bin/linguist - from package: qt-devel

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

On Debian possible default full paths are:

/usr/lib/x86_64-linux-gnu/qt4/bin/linguist - from package: qt4-dev-tools
/usr/bin/linguist - from package: qtchooser
/usr/lib/x86_64-linux-gnu/qt5/bin/linguist - from package: qttools5-dev-tools

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

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