The Linux Programming Interface

SOLUTIONS TO

SELECTED EXERCISES

Chapter 5

5-3. A solution is provided in the file fileio/atomic_append.c in the source code

distribution for this book. Here is an example of the results that we see when we

run this program as suggested:

$ ls -l f1 f2

-rw------- 1 mtk users 2000000 Jan 9 11:14 f1

-rw------- 1 mtk users 1999962 Jan 9 11:14 f2

Because the combination of lseek() plus write() is not atomic, one instance of the

program sometimes overwrote bytes written by the other instance. As a result, the file

f2 contains less than 2 million bytes.

5-4. A call to dup() can be rewritten as:

fd = fcntl(oldfd, F_DUPFD, 0);