Dirent

Dirent, short for directory entry, is a portable API used by POSIX-compliant systems to read the contents of a directory. It is defined in the dirent.h header and centers on two main concepts: the DIR type, which represents an open directory stream, and the struct dirent, which represents a single directory entry. The d_name field stores the entry name, and many implementations also provide d_ino (inode number) and d_type (the entry’s file type, such as DT_DIR or DT_REG). The exact fields and their availability can vary between platforms; some fields may be absent or require additional checks.

The standard operations are opendir, readdir, and closedir. opendir opens a directory stream and returns a DIR*; readdir reads successive dirent records from that stream until NULL is returned, indicating end of entries or an error. closedir closes the stream. Additional functions include rewinddir (to restart reading from the beginning) and seekdir/telldir (to reposition within the stream). Some systems offer scandir, a higher-level function that reads, filters, and sorts entries into an array of dirent pointers. Readdir may return entries in any order, and entries “.” and “..” are typically included unless filtered by the caller.

Portability and caveats: the dirent interface is defined by POSIX and is widely implemented on Linux, BSD, macOS, and other UNIX-like systems. However, the availability of certain fields (notably d_type) and the exact layout of struct dirent can vary, so portable code often checks for feature support and may fallback to stat to determine entry types.

Example usage pattern: open a directory with opendir, iterate with readdir to process each entry by name, and finally close with closedir.