gmt_shell_functions.sh: 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/gmt_shell_functions.sh - 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/gmt_shell_functions.sh - from package: GMT

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

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