asciidoctor-safe: 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/asciidoctor-safe - from package: rubygem-asciidoctor
/usr/lib/ruby/gems/1.8/gems/asciidoctor-0.1.3/bin/asciidoctor-safe - from package: rubygem-asciidoctor

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

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