fgrep: 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:

/bin/fgrep - from package: grep

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

On Debian possible default full paths are:

/bin/fgrep - from package: grep

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

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