fastagrep.sh: 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/fastagrep.sh - from package: mmseq

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

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