kchmviewer: 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 - from package: kchmviewer

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

On Debian possible default full paths are:

/usr/bin/kchmviewer - from package: kchmviewer

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

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