Beefy Boxes and Bandwidth Generously Provided by pair Networks
Syntactic Confectionery Delight
 
PerlMonks  

Re^3: read file line by line then do something and write to same file

by oiskuu (Hermit)
on Jun 16, 2014 at 19:36 UTC ( #1090066=note: print w/ replies, xml ) Need Help??


in reply to Re^2: read file line by line then do something and write to same file
in thread read file line by line then do something and write to same file

A cursory strace perl -pi reveals a more sloppy pattern than described, however. I see open/unlink/open/read+write/close/close. The unlinked source file is still readable; it gets released upon close.

A relatively safe update sequence is: mkstemp/read+write/fsync/rename. The final rename is atomic, but that itself does not prevent races with multiple updaters (of course).

  • Comment on Re^3: read file line by line then do something and write to same file

Replies are listed 'Best First'.
Re^4: read file line by line then do something and write to same file
by davido (Archbishop) on Jun 16, 2014 at 19:44 UTC

    Yes, I believe you're correct regarding the strace. I recall now that the documentation is not 100% truthful as to what is happening behind the scenes. If you use -i.bak instead of -i, you'll probably see an open/rename/open/read+write/close/close instead of open/unlink...


    Dave

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://1090066]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others about the Monastery: (5)
As of 2016-06-25 00:59 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    My preferred method of making French fries (chips) is in a ...











    Results (322 votes). Check out past polls.