So I've been playing with ImageMagick to batch process psd files into
flattened jpgs. I have a bash script that runs a for loop with
"convert" on a directory. What I have noticed is that in xosview on my
Dual Intel Hyper Threaded box ( shows up as 4 cpu's cause of the HT ),
only one ( or one half? ) CPU is doing all the work. Makes sense
because of the whole user space kernel space thing and I don't really
need both CPU's working on pieces of the same image anyway.
What I would like though is a way to fork multiple children in the loop
to start additional instances of convert until 4 are active. Then wait
until one exits and then start on the next image. 4 active converts
always until all the images are processed.
i.e.
mbranda:~> pstree
├─kdeinit─┬
│ ├─konsole───bash───image_resize.sh─┬─convert
|─convert
|─convert
|─convert
Right now I just create 4 different dirs and run 4 instances of the
shell script ( which calls convert ) on them. This makes the batching
of a few hundred images go much faster. I know there's got to be a way
to fork more instances and count how many are active. I figure the for
loop will have to be smart in some way to fork and move on to the next
image in $dir until the max of 4 instances is reached.
I see
mbranda:~> apropos fork
fork (2) - create a child process
vfork (2) - create a child process and block parent
fork (3p) - create a new process
vfork (3p) - create a new process; share virtual memory
Any ideas or suggestions? Anybody actually use the fork command in a
script before?
Thanks!
Mike Branda Jr.
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