vcd2fst: 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/vcd2fst - from package: gtkwave

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

On Debian possible default full paths are:

/usr/bin/vcd2fst - from package: gtkwave

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

Error in other languages:
vcd2fst: bevel nie gevind nie
vcd2fst: comandă negăsită
vcd2fst: comando não encontrado
vcd2fst: commande introuvable
vcd2fst: command not found
vcd2fst: käsku ei ole
vcd2fst: không tìm thấy lệnh
vcd2fst: komanda nerasta
vcd2fst: Kommando nicht gefunden.
vcd2fst: kommandot finns inte
vcd2fst: komut yok
vcd2fst: nie znaleziono polecenia
vcd2fst: níor aimsíodh an t-ordú
vcd2fst: no se encontró la orden
vcd2fst: no s'ha trobat l'ordre
vcd2fst: opdracht niet gevonden
vcd2fst: parancs nem található
vcd2fst: perintah tidak ditemukan
vcd2fst: príkaz nenájdený
vcd2fst: příkaz nenalezen
vcd2fst: команда не найдена
vcd2fst: командата не е открита
vcd2fst: 命令找不到
vcd2fst: コマンドが見つかりません