pshistogram: 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/pshistogram - from package: GMT

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

On Debian possible default full paths are:

/usr/lib/gmt/bin/pshistogram - from package: GMT

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

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