qli: 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:

/usr/bin/qli - from package: firebird

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

On Debian possible default full paths are:

/usr/bin/qli - from package: firebird2.5-classic-common
/usr/bin/qli - from package: firebird2.5-super

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

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