csplain: 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/csplain - from package: texlive

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

On Debian possible default full paths are:

/usr/bin/csplain - from package: texlive-lang-czechslovak

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

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