POSIX:sys/stat

lastmod 2018-08-17created 2016-05-0510 edits

Methods

int    chmod(const char *, mode_t);
int    fchmod(int, mode_t);
int    fstat(int, struct stat *);
int    lstat(const char *, struct stat *);
int    mkdir(const char *, mode_t);
int    mkfifo(const char *, mode_t);
int    mknod(const char *, mode_t, dev_t);
int    stat(const char *, struct stat *);
mode_t umask(mode_t);

check macros

• S_ISDIR: directory
• S_ISREG: regular file
• S_ISCHR: character device
• S_ISBLK: block device
• S_ISFIFO: FIFO
• S_ISLNK: symbolic link
• S_ISSOCK: socket

Directory exists

• Stackoverflow: Checking if a directory exists in Unix (system call)

#include <sys/stat.h>
struct stat sb;
if (stat(pathname, &sb) == 0 && S_ISDIR(sb.st_mode))
{
    ...it is a directory...
}

Windows & MinGW version

• Stackoverflow: Error: identifier “_S_IFDIR” is undefined
• MSDN: _stat structure st_mode field constants

• _S_IFMT: file type mask
• _S_IFDIR: directory
• _S_IFCHR: character special (indicates a device if set)
• _S_IFREG: regular
• _S_IREAD: read permission, owner
• _S_IWRITE: write permission, owner
• _S_IEXEC: execute/search permission, owner

mode_t

• How to use mkdir() from sys/stat.h
• File system permissions

sys/stat.h provides you with several integers you can bytewise-OR (|) together to create your mode_t:

• User: S_IRUSR (read), S_IWUSR (write), S_IXUSR (execute)
• Group: S_IRGRP (read), S_IWGRP (write), S_IXGRP (execute)
• Others: S_IROTH (read), S_IWOTH (write), S_IXOTH (execute)

Additionally, some shortcuts are provided (basically a bitwise-OR combination of the above

• Read + Write + Execute: S_IRWXU (User), S_IRWXG (Group), S_IRWXO (Others)
• DEFFILEMODE: Equivalent of 0666 = rw-rw-rw-
• ACCESSPERMS: Equivalent of 0777 = rwxrwxrwx Therefore, to give only the user rwx (read+write+execute) rights whereas group members and others may not do anything, you can use any of the following mkdir() calls equivalently:

mkdir("mydir", S_IRUSR | S_IWUSR | S_IXUSR);
mkdir("mydir", S_IRWXU);

In order to give anyone any rights (mode 0777 = rwxrwxrwx), you can use any of the following calls equivalently:

mkdir("mydir", S_IRUSR | S_IWUSR | S_IXUSR | S_IRGRP | S_IWGRP | S_IXGRP | S_IROTH | S_IWOTH | S_IXOTH);
mkdir("mydir", S_IRWXU | S_IRWXG | S_IRWXO);
mkdir("mydir", ACCESSPERMS);

Favorite site

• stat(2) - Linux man page
• The Single UNIX ® Specification, Version 2 - sys/stat.h
• GNU libc: 14.9.3 Testing the Type of a File
• [Recommended] Getting file status information - stat, fstat, and lstat Functions ¹
• C language system programming: files and directories

Source code

• Source to sys/stat.h
• Mingw32 sys/stat.h

References