shpwkb: 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/shpwkb - from package: shapelib

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

On Debian possible default full paths are:

/usr/bin/shpwkb - from package: shapelib

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

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