v.build.polylines: command not found

Have You tried accessing the binary with the full path?

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/lib64/grass-6.4.4/bin/v.build.polylines - from package: grass

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

On Debian possible default full paths are:

/usr/lib/grass64/bin/v.build.polylines - from package: grass-core

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