g-ir-doc-tool: 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/g-ir-doc-tool - from package: gobject-introspection

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

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