tcsh: 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:

/bin/tcsh - from package: tcsh

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

On Debian possible default full paths are:

/bin/tcsh - from package: tcsh
/usr/bin/tcsh - from package: tcsh

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

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