The tee command reads its standard input until end-of-file, writing a copy of the input to standard output and to the file named in its command-line argument. (We show an example of the use of this command when we discuss FIFOs in Section 44.7.) Implement tee using I/O system calls. By default, tee overwrites any existing file with the given name. Implement the –a command-line option (tee –a file), which causes tee to append text to the end of a file if it already exists. (Refer to Appendix B for a description of the getopt() function, which can be used to parse command-line options.)
see 1_tee.c
Write a program like cp that, when used to copy a regular file that contains holes(sequences of null bytes), also creates corresponding holes in the target file.
For creating file with holes:
I use create_holes.c create one file with holes named file_with_holes.bin. (I use fseek create hole.But the easiest way to get one file with holes is just producing one executable file(e.g., gcc a.c -o a)
You can use du(actul disk usage,unit:kilobyte) and du -b(logical file size, unit: byte) check files with holes.
cp implementation: see 2_cp.c