Pause a running script in Mac terminal and then resume later

If you're using BASH as the shell (which is the default shell on a Mac), you can use BASH's built in job control capabilities.

If the script is running in the foreground of your terminal, you can press Control-Z to pause the script. This will suspend the running of the script.

To restart it, type jobs and you'll see the suspended job listed there. Type fg or more specific fg %x where x is the number of the suspended job.

$ test.pl   # Test script (prints out Foo every two seconds
Foo!
Foo!
^Z
$  # Job has been suspended
$ jobs
[1] + Stopped                  ./test.pl
$ fg %1  #Restarts Job #1
Foo!

The Control-Z key that suspends the job is the default, but could be modified. The stty can change this and will show you the current default:

$ stty -a     
speed 9600 baud; 40 rows; 120 columns;
lflags: icanon isig iexten echo echoe -echok echoke -echonl echoctl
        -echoprt -altwerase -noflsh -tostop -flusho pendin -nokerninfo
        -extproc
iflags: -istrip icrnl -inlcr -igncr ixon -ixoff ixany imaxbel iutf8
        -ignbrk brkint -inpck -ignpar -parmrk
oflags: opost onlcr -oxtabs -onocr -onlret
cflags: cread cs8 -parenb -parodd hupcl -clocal -cstopb -crtscts -dsrflow
        -dtrflow -mdmbuf
cchars: discard = ^O; dsusp = ^Y; eof = ^D; eol = <undef>;
        eol2 = <undef>; erase = ^H; intr = ^C; kill = ^U; lnext = ^V;
        min = 1; quit = ^\; reprint = ^R; start = ^Q; status = ^T;
        stop = ^S; susp = ^Z; time = 0; werase = ^W;

You can see the very last line has susp = ^Z. This is the key that will suspend your script. In this case, it's Control-Z.

You can also use the bg command to make a suspended job run in the background. However, that background job will terminate when you close the shell/Terminal Window unless you had prepended nohup to the front of the command.

Find the process ID of the running script.

To stop (or what you refer to as pause) the script, say:

kill -SIGSTOP PID

To resume the stopped (or paused) process, say:

kill -SIGCONT PID

(where PID refers to the numeric process ID.)