Splitsxiv

#!/usr/bin/env python
""" Serially invoke sxiv -i, splitting up a filelist (read from stdin) into chunks of N items.

Intended to simplify processing a large list of images, where you may wish to mark many and do operations on them,
by limiting the number you need to deal with at once.

Secondarily, prevents a situation from developing in which sxiv eats up all the memory,
presumably allocating it to thumbnails.
This occurs at about 10000 images, on the author's machine with 4Gb memory.

Syntax:
    splitsxiv [<chunksize> [sxiv arguments]]

chunksize defaults to 256. If you want to specify arguments to sxiv, you must specify chunksize.

"""

import sys
from subprocess import Popen, PIPE

chunksize = 256
sxiv_args = []

try:
    chunksize = int(sys.argv[1])
    sxiv_args = sys.argv[2:]
except IndexError:
    pass

if chunksize < 1:
    print('Chunksize %d invalid, must be greater than zero.' % chunksize)
    sys.exit(1)

# Enforce -i
sxiv_args.append('-i')

sxiv = Popen(['sxiv'] + sxiv_args, stdin=PIPE)
count = 0
total = 0
nchunks = 1

for line in sys.stdin:
    sxiv.stdin.write(line.encode('utf8'))
    count += 1
    total += 1
    if count == chunksize:
        sxiv.stdin.flush()
        sxiv.stdin.close()
        sxiv.wait()
        sxiv = Popen(['sxiv'] + sxiv_args, stdin=PIPE)
        nchunks += 1
        count = 0

sxiv.stdin.flush()
sxiv.stdin.close()
sys.stdout.write('splitsxiv: %d chunks processed with chunksize=%d,'
                 ' total %d files processed\n' % (nchunks, chunksize, total))