lstat() — Get status of file or symbolic link

Standards

Standards / Extensions	C or C++	Dependencies
z/OS® UNIX XPG4.2 Single UNIX Specification, Version 3	both

Format

#define _POSIX1_SOURCE 2
#include <sys/stat.h>

int lstat(const char *__restrict__ pathname, struct stat *__restrict__ buf);

General description

Gets status information about a specified file and places it in the area of memory pointed to by the buf argument. You do not need permissions on the file itself, but you must have search permission on all directory components of the pathname.

If the named file is a symbolic link, lstat() returns information about the symbolic link itself.

The information is returned in the following stat structure, defined in the sys/stat.h header file.

Table 1. Elements of stat Structure
Structure	Description
mode_t st_mode	A bit string indicating the permissions and privileges of the file. Symbols are defined in the sys/stat.h header file to refer to bits in a `mode_t` value; these symbols are listed in chmod() — Change the mode of a file or directory.
ino_t st_ino	The serial number of the file.
dev_t st_dev	The numeric ID of the device containing the file.
nlink_t st_nlink	The number of links to the file.
uid_t st_uid	The numeric user ID of the file's owner.
gid_t st_gid	The numeric group ID of the file's group.
off_t st_size	For regular files, the file's size in bytes. For symbolic links, the length of the pathname contained therein not counting the trailing NULL. For other kinds of files, the value of this field is unspecified.
time_t st_atime	The most recent time the file was accessed.
time_t st_ctime	The most recent time the status of the file was changed.
time_t st_mtime	The most recent time the contents of the file were changed.

Values for time_t are given in terms of seconds that have elapsed since epoch.

If the named file is a symbolic link, lstat() updates the time-related fields before putting information in the stat structure.

You can examine properties of a mode_t value from the st_mode field by using a collection of macros defined in the sys/modes.h header file. If mode is a mode_t value, and genvalue is an unsigned int value from the stat structure, then:

S_ISBLK(mode): Is nonzero for block special files.
S_ISCHR(mode): Is nonzero for character special files.
S_ISDIR(mode): Is nonzero for directories.
S_ISEXTL(mode,genvalue): Is nonzero for external links.
S_ISFIFO(mode): Is nonzero for pipes and FIFO special files.
S_ISLNK(mode): Is nonzero for symbolic links.
S_ISREG(mode): Is nonzero for regular files.
S_ISSOCK(mode): Is nonzero for sockets.

If lstat() successfully determines all this information, it stores it in the area indicated by the buf argument.

Large file support for z/OS UNIX files: Large z/OS UNIX files are supported automatically for AMODE 64 C/C++ applications. AMODE 31 C/C++ applications must be compiled with the option LANGLVL(LONGLONG) and define the _LARGE_FILES feature test macro before any headers are included to enable this function to operate on z/OS UNIX files that are larger than 2 GB in size. File size and offset fields are enlarged to 63 bits in width. Therefore, any other function operating on the file is required to define the _LARGE_FILES feature test macro as well.

Returned value

If successful, lstat() returns 0.

If unsuccessful, lstat() returns -1 and sets errno to one of the following values:

Error Code: Description
EACCES: The process does not have search permission on some component of the pathname prefix.
EINVAL: buf contains a NULL.
EIO: Added for XPG4.2: An I/O error occurred while reading from the file system.
ELOOP: A loop exists in symbolic links. This error is issued if the number of symbolic links encountered during resolution of the pathname argument is greater than POSIX_SYMLOOP.
ENAMETOOLONG: pathname is longer than PATH_MAX characters or some component of pathname is longer than NAME_MAX characters while _POSIX_NO_TRUNC is in effect. For symbolic links, the length of the pathname string substituted for a symbolic link exceeds PATH_MAX. The PATH_MAX and NAME_MAX values can be determined through pathconf().
ENOENT: There is no file named pathname, or pathname is an empty string.
ENOTDIR: A component of the pathname prefix is not a directory.
EOVERFLOW: The file size in bytes or the number of blocks allocated to the file or the file serial number cannot be represented correctly in the structure pointed to by buf.
Note: Starting with z/OS V1.9, environment variable _EDC_EOVERFLOW can be used to control behavior of lstat() with respect to detecting an EOVERFLOW condition for z/OS UNIX files. By default, lstat() will not set EOVERFLOW when the file size can not be represented correctly in structure pointed to by buf. When _EDC_EOVERFLOW is set to YES, lstat() will check for an overflow condition.

Example

CELEBL12

⁄* CELEBL12

   This example provides status information for a file.

 *⁄
#define _POSIX_SOURCE
#include <fcntl.h>
#include <sys⁄types.h>
#include <sys⁄stat.h>
#include <unistd.h>
#undef _POSIX_SOURCE
#include <stdio.h>
#include <time.h>

main() {
  char fn[]="temp.file", ln[]="temp.link";
  struct stat info;
  int fd;

  if ((fd = creat(fn, S_IWUSR)) < 0)
    perror("creat() error");
  else {
    close(fd);
    if (link(fn, ln) != 0)
      perror("link() error");
    else {
      if (lstat(ln, &info) != 0)
        perror("lstat() error");
      else {
        puts("lstat() returned:");
        printf("  inode:   %d\n",   (int) info.st_ino);
        printf(" dev id:   %d\n",   (int) info.st_dev);
        printf("   mode:   %08x\n",       info.st_mode);
        printf("  links:   %d\n",         info.st_nlink);
        printf("    uid:   %d\n",   (int) info.st_uid);
        printf("    gid:   %d\n",   (int) info.st_gid);
        printf("created:   %s",           ctime(&info.st_createtime));
      }
      unlink(ln);
    }
    unlink(fn);
  }
}

Output

lstat() returned:
  inode:   3022
 dev id:   1
   mode:   03000080
  links:   2
    uid:   25
    gid:   500
created:   Fri Jun 16 15:00:00 2001