File pointer/handle (File *), file descriptor (FD), and file path (filepath) Conversion

From http://blog.csdn.net/jenghau/article/details/5532265

FILE pointer/handle (FILE *), FILE descriptor (fd), and FILE path (filepath) Conversion

 

Recently, programming in linux often requires operations on some files. Sometimes, you need to convert the FILE pointer/handle (FILE *), FILE descriptor (fd), and FILE path (filepath) to meet the actual programming needs.

Now we can simply sort it out. As follows.

 

 

1: The file path file descriptor should be unique. The file pointer (value) is not unique, but the object to which it points should also be unique.
2: FILE * contains fd information and IO buffer. Therefore, it can be understood that FILE * is an encapsulation of fd and a standard form of C, therefore, FILE * is more suitable for cross-platform use than fd, and fopen should be used more than open.

 

3: Conversion

FILE Path to FILE pointer: filepath -- fopen () --> FILE *;
File Path to file descriptor: filepath -- open () -- fd;

 

FILE descriptor to FILE pointer: fd -- fdopen () --> FILE *;
File descriptor to file path: fd -- readlink (/proc/% getpid ()/fd/% fd ") --> filepath; // This is a" curve saving"

FILE pointer to FILE descriptor: FILE * -- fileno () ---> fd;
FILE pointer to FILE path: FILE *---??? --- PATH; // The direct conversion method is not found yet. Please add.