Beginning Linux Programming, 4th Edition

Chapter 3

Working with Files

In this chapter, you look at Linux files and directories and how to manipulate them. You learn how to create files, open them, read, write, and close them. You also learn how programs can manipulate directories (to create, scan, and delete them, for example). After the preceding chapter’s diversion into shells, you now start programming in C.

Before proceeding to the way Linux handles file I/O, we review the concepts associated with files, directories, and devices. To manipulate files and directories, you need to make system calls (the UNIX and Linux parallel of the Windows API), but there also exists a whole range of library functions, the standard I/O library (stdio), to make file handling more efficient.

We spend the majority of the chapter detailing the various calls to handle files and directories. So this chapter covers various file-related topics:

• Files and devices
• System calls
• Library functions
• Low-level file access
• Managing files
• The standard I/O library
• Formatted input and output
• File and directory maintenance
• Scanning directories
• Errors
• The /proc file system
• Advanced topics: fcntl and mmap

Linux File Structure

“Why,” you may be asking, “are we covering file structure? I know about that already.” Well, as with UNIX, files in the Linux environment are particularly important, because they provide a simple and consistent interface to the operating system services and devices. In Linux, everything is a file. Well, almost!

This means that, in ...