Running multiple background processes in script

Question

I have a shell script of the following format :

cd /path/a/
make 
cd /path/b/
make
cd /path/c/
make

Each of the make commands are independent of each other in different directories. I would like to speed up the script by running the different make commands in background using '&'

cd /path/a/
make & 
cd /path/b/
make &
cd /path/c/
make &

Would this work? While the first make command is running, the directory has changed to /path/b/ in the next line. Will this affect the first make commend in the background?

Edit: I am doubtful if this method would actually make this process faster, and wonder if these need to be run in separate processes.

tivn · Accepted Answer · 2015-05-06 22:10:37Z

2

That should be fine. make also accept -C option to change its directory before reading the makefile. So you can do like this as well:

make -C /path/a/ &
make -C /path/b/ &
make -C /path/c/ &

answered May 6, 2015 at 22:10

tivn

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2 Comments

Nikhil Over a year ago

Thanks. These make commands are truly running in parallel right... and not just one after the other in background?

tivn Over a year ago

It will certainly run in parallel if you have multi processor. With single processor this is going to be time-sliced parallel.

Trent Small · Accepted Answer · 2015-05-06 22:04:27Z

1

I believe that make takes a -f command line argument where you can simply specify the makefile you want. So, this should work: make -f /path/a/makefile & make -f /path/b/makefile & make -f /path/c/makefile &

answered May 6, 2015 at 22:04

Trent Small

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2 Comments

Nikhil Over a year ago

This would work only if the make file would use absolute paths everywhere right

Trent Small Over a year ago

Ah, right. Looks like tivn's answer is more relevant in the case of relative paths.

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