View Full Version : [all variants] What's faster, file globbing or a loop?
July 5th, 2008, 09:31 PM
If I have a set of files, say file1, file2, file3, ..., file9
Which would be faster?
for i in `seq 0 99`; do
Obviously the filename expansion is neater syntactically, but is the loop faster? In general how does the expansion work... is it an internal loop of some sort?
July 5th, 2008, 09:40 PM
I'm leaning towards the first one, since the way searches like the later 2 work as far as I can imagine would be something similar to
for i in `ls`; do
if [ i =~ file[0-9][0-9] ]; then
July 5th, 2008, 10:22 PM
I expect that
1 slower than 2 = 3
Why don't you make a little experiment and report back your results. See
Create a lot of files then use
time cat *
July 5th, 2008, 10:35 PM
Yeah, that's what I was thinking. It would either be some sort of loop or a series of tests.
I guess it depends on the situation. For example if the only files in a directory were file20 and file30 then using globbing would probably be more efficient than writing my own loop to search for file00 to file99
July 6th, 2008, 12:00 AM
When you use cat file?? then you are only starting a process 1 time and passing it lots of arguments. The looping over the different file names will be done internal to the single running process.
When you use the for... loop, you are starting (and ending) a new process for each file. Probably the difference would be inconsequential for a modern system and a reasonable number of files, but my bet would be that the for... loop would take longer.
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