gsl-histogram: 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/gsl-histogram - from package: gsl

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

On Debian possible default full paths are:

/usr/bin/gsl-histogram - from package: gsl-bin

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

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