xclip-copyfile: 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/xclip-copyfile - from package: xclip

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

On Debian possible default full paths are:

/usr/bin/xclip-copyfile - from package: xclip

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

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