kchmviewer-qt: 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/kchmviewer-qt - from package: kchmviewer-qt

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

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