trjcat: 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/trjcat - from package: gromacs

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

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