for a in bar do for b in 1000000 do montage -geometry 500 $a-$b-*-${0..20000..1000}.png \ $a-$b-${0..20000..1000}-final.jpg done done I'm unable to get all the images with number 0 1000 2000 ... 20000 using $(0..20000.1000) .
Is there an other way in shell to do this?
There must be no $ before {START..END..STEP}
% echo -{0..20000..1000}- -0- -1000- -2000- -3000- -4000- -5000- -6000- -7000- -8000- -9000- -10000- -11000- -12000- -13000- -14000- -15000- -16000- -17000- -18000- -19000- -20000- That being said, you need a loop to go over these numbers. The word containing a range is just replaced by its expansion. That means the command line is not called for each element alone, but for all of them together. It also means, that, even if you are using the same range twice, their expansion will not conveniently be combined.
Compare
% echo start a-{1..3}-b A-{1..3}-B end start a-1-b a-2-b a-3-b A-1-B A-2-B A-3-B end and
% for n in {1..3}; do echo start a-$n-b A-$n-B end; done start a-1-b A-1-B end start a-2-b A-2-B end start a-3-b A-3-B end So in your example instead of
montage -geometry 500 $a-$b-*-${0..20000..1000}.png \ $a-$b-${0..20000..1000}-final.jpg you probably want to do
for n in {0..20000..1000}; do montage -geometry 500 $a-$b-*-$n.png $a-$b-$n-final.jpg done 
#!/usr/bin/env python import os file_names= ["a","b"] ranges = list(xrange(0, 20000, 1000)) l_s = list() for f in range(0, len(file_names)): for a in range(0, len(ranges)): stringing = str(file_names[f]) + "--1000000-0-0-0-1-" + str(ranges[a]) + ".log.png" l_s.append(stringing) final = " ".join(l_s) foo = "montage -geometry 500 " + str(final) + " " + str(file_names[f])+ "-final.jpg" os.system(foo) 
