Stat (Unix)

stat() is a Unix system call that returns file attributes about an inode. The semantics of stat() vary between operating systems. As an example, Unix command ls uses this system call to retrieve information on files that includes:

stat appeared in Version 1 Unix. It is among the few original Unix system calls to change, with Version 4's addition of group permissions and larger file size.

The C POSIX library header sys/stat.h, found on POSIX and other Unix-like operating systems, declares the stat() functions, as well as related function called fstat() and lstat(). The functions take a struct stat buffer argument, which is used to return the file attributes. On success, the functions return zero, and on error, −1 is returned and errno is set appropriately.

The stat() and lstat() functions take a filename argument. If the file is a symbolic link, stat() returns attributes of the eventual target of the link, while lstat() returns attributes of the link itself. The fstat() function takes a file descriptor argument instead, and returns attributes of the file that it identifies.

The family of functions was extended to implement large file support. Functions named stat64(), lstat64() and fstat64() return attributes in a struct stat64 structure, which represents file sizes with a 64-bit type, allowing the functions to work on files 2 GiB and larger. When the _FILE_OFFSET_BITS macro is defined to 64, these 64-bit functions are available under the original names.

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