ssgrep: 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/ssgrep - from package: gnumeric

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

On Debian possible default full paths are:

/usr/bin/ssgrep - from package: gnumeric

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

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