bitlbee: 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/sbin/bitlbee - from package: bitlbee

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

On Debian possible default full paths are:

/usr/sbin/bitlbee - from package: bitlbee-libpurple
/usr/sbin/bitlbee - from package: bitlbee

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

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