Argthtjtr

I have 2 questions about starting the processes in the background:

1. 
   

   Why does starting a process in the background like so:

   
   
   

   ./my_program &

   
   
   

   (my_program have exe permission set of course) doesn't make the
   bash to print the command prompt like any other commands? It just
   left a empty new line with blinking cursor.

   
   


2. 
   

   When i run a next new processes in the background bash displays sth.
   like that:

   
   
   

   ./my_program &
[30] 1439
[27] Done ./my_program
[28] Done ./my_program
[29] Done ./my_program

   
   
   

   does this mean that starting
   another extra processes in the background makes the system to
   display an info about the previews processes ([27], [28], [29]
   lines) as long as the currently started) ([30] line)?

   
   

1. 
   

   This shouldn't happen. When you run a command in the background bash usually just prints the job number and pid (see below) and then drops back to a command prompt.

   
   
   

   The only reason I know of that leads bash to leave you with a new line in this situation is if your command doesn't actually exist, as it will somehow give the error message for that after printing PS1:

   
   
   

   $ nonexistant_command &
   
   [1] 13856
   
   $
   
   nonexistant_command: command not found
   
   <empty line with blinking cursor here>
   
   

   
   
   

   Whatever the cause may be, pressing enter while on this empty line should print a new line with your usual prompt (and, possibly, the message that the job you just spawned finished; see below).

   
   


2. 
   

   The additional output you see is bash telling you about current background jobs:

   
   
   

   First, it tells you the current job number of any newly created background process together with its pid, like so:

   
   
   

   $ some_command
   
   [1] 1234
   
   

   
   
   

   This means that the command some_command is now being run with the pid 1234 as job 1.

   
   
   

   Once a background job finishes, bash will notify you of this the next time it prints a command prompt (whether it be because you spawned another background process, ran a command in the foreground or simply pressed enter with an empty command line) by printing a message like this:

   
   
   

   [1]  Done                    some_command
   
   

   
   
   

   This means that the job with the number 1 which ran some_command has now finished.

   
   
   

   To find out what background jobs bash is currently tracking, you can use the jobs builtin like so:

   
   
   

   $ jobs
   
   [1]  Running                 some_command &
   
   [2]  Running                 some_other_command &
   
   

   
   
   

   To bring a job to the foreground, you can use fg:

   
   
   

   $ fg 2
   
   some_other_command
   
   

   
   
   

   For more info on this, try help jobs