xchm: 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/xchm - from package: xchm

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

On Debian possible default full paths are:

/usr/bin/xchm - from package: xchm

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

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