clang-format: 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/clang-format - from package: clang

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

On Debian possible default full paths are:

/usr/lib/llvm-3.4/bin/clang-format - from package: clang-format-3.4
/usr/lib/llvm-3.5/bin/clang-format - from package: clang-format-3.5

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

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