jobs

Consider the following code : count.c .

Compile and run it to get something like this

$ gcc count.c -o count
$ ./count 2
./count 2
 i=1 at 0 sec in process 12917 
 i=2 at 2 sec in process 12917 
 i=3 at 4 sec in process 12917 
 i=4 at 6 sec in process 12917 
 i=5 at 8 sec in process 12917 

... typing control-C when we're tired of seeing it run.

We can also run it "in the background", meaning it detaches stdin from the terminal but continues on, and still outputs to the terminal ...

And we can start another.

Here are some things to try. (Check the man pages and/or google for options; there are many variations.)

• jobs shows the current running pipes
• ps shows the current processes
• kill -9 // send a TERM (terminate) signal (same as control-C)
• type control-Z (suspend)
• type control-C (stop)
• %2 // where 2 is a job number ; reconnect that to the terminal
• %string // same; looks for "string" as the start of a previous job command
• command & // run a command in the background

Concepts to understand : foreground, background, "attached to terminal", suspend, ...

playing around

jim@jupyter:procedures$ jobs
jim@jupyter:procedures$ ps
  PID TTY          TIME CMD
11044 pts/16   00:00:00 bash
13228 pts/16   00:00:00 ps
jim@jupyter:procedures$ ./count 10 &
[1] 13232
jim@jupyter:procedures$  i=1 at 0 sec in process 13232 

jim@jupyter:procedures$ ./count 5 &
[2] 13235
jim@jupyter:procedures$  i=1 at 0 sec in process 13235 

jim@jupyter:procedures$  i=2 at 10 sec in process 13232 
 i=2 at 5 sec in process 13235 
 i=3 at 10 sec in process 13235 
 i=3 at 20 sec in process 13232 

jim@jupyter:procedures$  i=4 at 15 sec in process 13235 

jim@jupyter:procedures$ jobs
[1]-  Running                 ./count 10 &
[2]+  Running                 ./count 5 &
jim@jupyter:procedures$  i=5 at 20 sec in process 13235 

jim@jupyter:procedures$  i=4 at 30 sec in process 13232 
 i=6 at 25 sec in process 13235 

jim@jupyter:procedures$  i=7 at 30 sec in process 13235 

jim@jupyter:procedures$ %1
./count 10
 i=5 at 40 sec in process 13232 
 i=8 at 35 sec in process 13235 
^Z
[1]+  Stopped                 ./count 10
jim@jupyter:procedures$ 
jim@jupyter:procedures$ jobs
[1]+  Stopped                 ./count 10
[2]-  Running                 ./count 5 &
jim@jupyter:procedures$  i=9 at 40 sec in process 13235 

jim@jupyter:procedures$ ps
  PID TTY          TIME CMD
11044 pts/16   00:00:00 bash
13232 pts/16   00:00:00 count
13235 pts/16   00:00:00 count
13256 pts/16   00:00:00 ps
jim@jupyter:procedures$  i=10 at 45 sec in process 13235 

jim@jupyter:procedures$ ps t
  PID TTY      STAT   TIME COMMAND
11044 pts/16   Ss     0:00 -bash
13232 pts/16   T      0:00 ./count 10
13235 pts/16   S      0:00 ./count 5
13257 pts/16   R+     0:00 ps t
jim@jupyter:procedures$  i=11 at 50 sec in process 13235 

jim@jupyter:procedures$  i=12 at 55 sec in process 13235 

jim@jupyter:procedures$  i=13 at 60 sec in process 13235 

jim@jupyter:procedures$ kill -9 1 i=14 at 65 sec in process 13235 
3235
jim@jupyter:procedures$ jobs
[1]+  Stopped                 ./count 10
[2]-  Killed                  ./count 5