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Top Forums UNIX for Dummies Questions & Answers Difference between file descriptor and file pointer Post 302402965 by karthigayan on Thursday 11th of March 2010 03:42:13 AM
Old 03-11-2010
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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.
 

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dup(2)								System Calls Manual							    dup(2)

NAME
dup - duplicate an open file descriptor SYNOPSIS
DESCRIPTION
fildes is a file descriptor obtained from a or system call. returns a new file descriptor having the following in common with the origi- nal: o Same open file (or pipe). o Same file pointer (i.e., both file descriptors share one file pointer). o Same access mode (read, write or read/write). o Same file status flags (see fcntl(2), The new file descriptor is set to remain open across system calls. See fcntl(2). The file descriptor returned is the lowest one available. RETURN VALUE
Upon successful completion, the file descriptor is returned as a non-negative integer. Otherwise, a value of -1 is returned and is set to indicate the error. ERRORS
fails if one or more of the following is true: fildes is not a valid open file descriptor. Request violates the maximum number of open file descriptors. AUTHOR
was developed by AT&T and HP. SEE ALSO
close(2), creat(2), dup2(2), exec(2), fcntl(2), open(2), pipe(2), privileges(5). STANDARDS CONFORMANCE
dup(2)
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