Changes to fopen function
The fopen function is usually used for opening a file and returning a file descriptor to that file. The concept of a file is very general in Unix, and by using the term file, we don't necessarily mean a file located on the filesystem. The fopen function has the following signatures:
FILE* fopen(const char *pathname, const char *mode); FILE* fdopen(int fd, const char *mode); FILE* freopen(const char *pathname, const char *mode, FILE *stream);
Code Box 12-2: Various signatures of the family of fopen functions
As you can see, all of the preceding signatures accept a mode input. This input parameter is a string that determines how the file should be opened. The following description in Shell Box 12-2 is obtained from the FreeBSD manual for the fopen function and explains how mode should be used:
$ man 3 fopen
...
The argument mode points to a string beginning with one of the following letters:
"r" Open for reading. The...