How to prevent a C++ program reading a file that is still being written to.?


 
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Top Forums Programming How to prevent a C++ program reading a file that is still being written to.?
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Old 06-26-2014
The only way to know the file has been completely written is to have the writing process signal success in some way. Because only the writing process knows if it has successfully written all the data supposed to be in the file. The receiving process can not infer that accurately because of failure conditions, so any method based on timestamps or something similar can not be guaranteed to work.

Period.

Renaming the file is probably the best way to do that.

There are some kludges you can use on Solaris using the utssys() call that will return the process IDs of process that have any file open, but that will just tell you the file is open and won't tell you why the process has the file open, nor why it closed it. Look at the "sys/utssys.h" header file.

If you can find the source code for the Solaris "fuser" utility, you can see an example of how to use it.

Or you can run the "fuser" utility in a subprocess using system() or popen().
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MICRODC(1)						      General Commands Manual							MICRODC(1)

NAME
microdc - A command-line based Direct Connect client SYNOPSIS
microdc [OPTION]... DESCRIPTION
microdc is a command-line based Direct Connect client that uses the GNU Readline library for user interaction. It was developed from ground up and does not depend on any other program. Despite the command-line user interface, microdc was designed to be user friendly and simple to use. OPTIONS
This program follows the usual GNU command line syntax, with long options starting with two dashes (`--'). -c, --config=FILE Read configuration script from FILE rather than ~/.microdc/config. -n, --no-config Do not read config file on startup. --help Show summary of options. --version Output version information and exit. --filelist_refresh_interval=NUMBER Local filelist refresh interval (in seconds). If set to zero, program runs in a special slave mode: it never updates the file list, just checks every minute if the filelist changes, and if so - reads it. This is pretty useful if you connect to several hubs and use same filelist. FILES
The following files are used by microdc (~ represents the current user's home directory): ~/.microdc/config This file is loaded on startup. It contains commands, one per line, that will be executed on startup. You can override loading of this file with --config and --no-config. ~/.microdc/history This is the command history file. It contains a list of commands that were typed and executed from the microdc prompt. It can safely be removed. REPORTING BUGS
Report bugs to <oskar@osk.mine.nu>. AUTHOR
The author of microdc and this manual page is Oskar Liljeblad <oskar@osk.mine.nu>. COPYRIGHT
Copyright (C) 2004, 2005 Oskar Liljeblad This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICU- LAR PURPOSE. microdc September 17, 2005 MICRODC(1)