fastx_reverse_complement: 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/fastx_reverse_complement - from package: fastx-toolkit

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

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