For cycle, process order


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# 1  
For cycle, process order

Hello,
I am running a script under ubuntu 16.04
I have no problem with the script. My question is general algorithm of for file command.
I just need to know how for file in *.txt process works.

Let's say, I wish to run the script by sorting filename:
Code:
for file in *.txt
do
"do something in alphabetical order"
done

or
Code:
for file in *.txt
do
"do something according to filesize in ascending direction"
done

or another way:
Code:
for file in *.txt
do
"do something in by recently updated file"
done

or
Code:
for file in *.txt
do
"do something by total string length of each filename in descending order"
done

In summarize: If we do not indicate any criteria, what's the default working method of for cycle ?
Thank you
Boris
# 2  
It's not the for cycle's feature but the way the shell expands the "glob"s using "pattern matching". man bash is your friend:

Quote:
Pathname Expansion
After word splitting, unless the -f option has been set, bash scans each word for the characters *, ?, and [. If one of these characters appears, then the word is regarded as a pattern, and replaced with an alphabetically sorted list of filenames matching the pattern.
For any other arrangement of the value list, additional measures must be taken.
This User Gave Thanks to RudiC For This Post:
# 3  
Why not check it by creating some files and doing for loop with a simple echo ?
Default order of things should be apparent from the output produced.

As for other requirements, it will have to be coded for each case specifically using if , case or both, piped to sort command or whatever.
Some like length of filename shell builtin can be used e.g. ${#i}

For sorting requirement per modified time a simple example for mtime change
Last modified file will be last printed on the screen.
Code assumes there are not comma , in filenames.
Code:
for i in *.txt; do printf "%s," $i ; stat -c %Y $i; done | sort -t, -k2

Hope that helps
Regards
Peasant.
These 2 Users Gave Thanks to Peasant For This Post:
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