grepcidr: 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 Debian possible default full paths are:

/usr/bin/grepcidr - from package: grepcidr

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

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