Wednesday, September 26, 2012

Simple Program to copy its input to output

This program copy anything to anything.Since the input and output can be redirected to any file or device.
   We can write a simple program to copy its input to output.we use low level I/O read and write system calls.we have collected function prototypes for the system calls into a file called syscalls.h.so we can include it in this program.but the name syscalls.h is not standard.In UNIX system "unistd.h" is used instead of "syscalls.h".The program code is below:














The parameter BUFSIZ is defined in "stdio.h"; Its value is  good size for the local system. if the file size is not a multiple of BUFSIZ, some read will return a smaller number of bytes to be written by write; the next call to read after that will return zero.

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