zbarcam: 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/zbarcam - from package: zbar

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

On Debian possible default full paths are:

/usr/bin/zbarcam - from package: zbar-tools

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

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