realcsh.c: 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 Debian possible default full paths are:

/usr/bin/realcsh.c - from package: binfmtc

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

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