s9cols: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/bin/s9cols - from package: scheme9

You may install the required package with command apt-get install {package}
Error in other languages:
s9cols: bevel nie gevind nie
s9cols: comandă negăsită
s9cols: comando não encontrado
s9cols: commande introuvable
s9cols: command not found
s9cols: käsku ei ole
s9cols: không tìm thấy lệnh
s9cols: komanda nerasta
s9cols: Kommando nicht gefunden.
s9cols: kommandot finns inte
s9cols: komut yok
s9cols: nie znaleziono polecenia
s9cols: níor aimsíodh an t-ordú
s9cols: no se encontró la orden
s9cols: no s'ha trobat l'ordre
s9cols: opdracht niet gevonden
s9cols: parancs nem található
s9cols: perintah tidak ditemukan
s9cols: príkaz nenájdený
s9cols: příkaz nenalezen
s9cols: команда не найдена
s9cols: командата не е открита
s9cols: 命令找不到
s9cols: コマンドが見つかりません