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Top Forums UNIX for Dummies Questions & Answers Difference between file descriptor and file pointer Post 302444882 by kvok on Friday 13th of August 2010 05:31:11 AM
Old 08-13-2010
Quote:
Originally Posted by karthigayan
File descriptor is an integer which is an index in the kernel on the opened files(Which is called file descriptor table).It is used to deal with the files . most of the functions like open,close,read using the file descriptors to deal with the files.

File pointer is a location with in the file.Which points the next character which going to read.
So shall I understand that the filedescriptor is number of amount connections for particular process/program which will be used ? and its predefined ?
 

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getdtablesize(2)						System Calls Manual						  getdtablesize(2)

NAME
getdtablesize() - get the size of the per-process file descriptor table SYNOPSIS
DESCRIPTION
The function returns the maximum number of file descriptors that can currently be stored in a process' file descriptor table. This maximum number is also known as the soft limit for open files, and can be adjusted up to the hard limit by calling The entries in the descriptor table are numbered with small integers starting at 0 (zero). The function returns the total number of file descriptors that a process can have open simultaneously. Each process is limited to a cur- rent maximum (soft limit) and a fixed upper bound (hard limit) of open file descriptors. This limit is at least 32. The system-defined limits are configurable. See the descriptions of the and kernel parameters in maxfiles_lim(5) and maxfiles(5), respectively, for informa- tion about changing the system-defined, per-process limit on open file descriptors. RETURN VALUES
The function returns the size of the descriptor table (soft limit), and is always successful. SEE ALSO
close(2), getrlimit(2), open(2), select(2), setrlimit(2), sysconf(2), maxfiles(5), maxfiles_lim(5). STANDARDS CONFORMANCE
getdtablesize(2)
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