stg-show: 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/stg-show - from package: stgit-contrib

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

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