Run a job in the background$ command &When it's done, the terminal prints[n]+    commandor [n]-    commandSo sometimes it's a plus and other times it's a minus following [n].What does plus/minus mean?
+/- after a job in the background is done
shell;background process;job control
They are to distinguish between current and previous job; the last job and the second last job for more than two jobs, with + for the last and - for the second last one.From man bash:The previous job may be referenced using %-.  If there is only a  single job, %+ and %- can both be used to refer to that job.  In  output pertaining to jobs (e.g., the output of the jobs command), the  current job is always flagged with a +, and the previous job with a   -.Example:$ sleep 5 &[1] 21795$ sleep 5 &[2] 21796$ sleep 5 &[3] 21797$ sleep 5 &[4] 21798$ jobs[1]   Running                 sleep 5 &[2]   Running                 sleep 5 &[3]-  Running                 sleep 5 &[4]+  Running                 sleep 5 &$ [1]   Done                    sleep 5[2]   Done                    sleep 5[3]-  Done                    sleep 5[4]+  Done                    sleep 5