sortm.sh: 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/share/doc/mh-book/examples/xmh/bin/sortm.sh - from package: mh-book

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

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