Get information about a file or directory, given a path
#include <sys/stat.h> int stat( const char * path, struct stat * buf ); int stat64( const char * path, struct stat64 * buf );
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
The stat() and stat64() functions obtain information about the file or directory referenced in path. This information is placed in the structure located at the address indicated by buf.
Here's the stat structure that's defined in <sys/stat.h>:
struct stat { #if _FILE_OFFSET_BITS - 0 == 64 ino_t st_ino; /* File serial number. */ off_t st_size; /* File size in bytes. */ #elif !defined(_FILE_OFFSET_BITS) || _FILE_OFFSET_BITS == 32 #if defined(__LITTLEENDIAN__) ino_t st_ino; /* File serial number. */ ino_t st_ino_hi; off_t st_size; off_t st_size_hi; #elif defined(__BIGENDIAN__) ino_t st_ino_hi; ino_t st_ino; /* File serial number. */ off_t st_size_hi; off_t st_size; #else #error endian not configured for system #endif #else #error _FILE_OFFSET_BITS value is unsupported #endif dev_t st_dev; /* ID of the device containing the file. */ dev_t st_rdev; /* Device ID. */ uid_t st_uid; /* User ID of file. */ gid_t st_gid; /* Group ID of file. */ time_t st_mtime; /* Time of last data modification. */ time_t st_atime; /* Time when file data was last accessed.*/ time_t st_ctime; /* Time of last file status change. */ mode_t st_mode; /* File types and permissions. */ nlink_t st_nlink; /* Number of hard links to the file. */ blksize_t st_blocksize; /* Size of a block used by st_nblocks. */ _int32 st_nblocks; /* Number of blocks st_blocksize blocks. */ blksize_t st_blksize; /* Preferred I/O block size for object. */ #if _FILE_OFFSET_BITS - 0 == 64 blkcnt_t st_blocks; /* No. of 512-byte blocks allocated for a file. */ #elif !defined(_FILE_OFFSET_BITS) || _FILE_OFFSET_BITS == 32 #if defined(__LITTLEENDIAN__) blkcnt_t st_blocks; /* No. of 512-byte blocks allocated for a file. */ blkcnt_t st_blocks_hi; #elif defined(__BIGENDIAN__) blkcnt_t st_blocks_hi; blkcnt_t st_blocks; #else #error endian not configured for system #endif #else #error _FILE_OFFSET_BITS value is unsupported #endif };
The access permissions for the file or directory are specified as a combination of bits in the st_mode field of a stat structure. These bits are defined in <sys/stat.h>, and are described below:
Owner | Group | Others | Permission |
---|---|---|---|
S_IRUSR | S_IRGRP | S_IROTH | Read |
S_IRWXU | S_IRWXG | S_IRWXO | Read, write, execute/search. A bitwise inclusive OR of the other three constants. (S_IRWXU is OR of IRUSR, S_IWSUR and S_IXUSR.) |
S_IWUSR | S_IWGRP | S_IWOTH | Write |
S_IXUSR | S_IXGRP | S_IXOTH | Execute/search |
The following bits define miscellaneous permissions used by other implementations:
Bit | Equivalent |
---|---|
S_IEXEC | S_IXUSR |
S_IREAD | S_IRUSR |
S_IWRITE | S_IWUSR |
The following bits are also encoded in the st_mode field:
The following symbolic names for the values of st_mode are defined for these file types:
The following macros test whether a file is of a specified type. The value m supplied to the macros is the value of the st_mode field of a stat structure. The macros evaluate to a nonzero value if the test is true, and zero if the test is false.
These macros test whether a file is of the specified type. The value of the buf argument supplied to the macros is a pointer to a stat structure. The macro evaluates to a nonzero value if the specified object is implemented as a distinct file type and the specified file type is contained in the stat structure referenced by the pointer buf. Otherwise, the macro evaluates to zero.
These macros manipulate device IDs:
The st_rdev member of the stat structure is a device ID that consists of:
Determine the size of a file:
#include <stdio.h> #include <stdlib.h> #include <sys/stat.h> int main( void ) { struct stat buf; if( stat( "file", &buf ) != -1 ) { printf( "File size = %d\n", buf.st_size ); } return EXIT_SUCCESS; }
Determine the amount of free memory:
#include <stdio.h> #include <stdlib.h> #include <sys/stat.h> int main () { struct stat buf; if ( stat( "/proc", &buf ) == -1) { perror ("stat" ); return EXIT_FAILURE; } else { printf ("Free memory: %d bytes\n", buf.st_size); return EXIT_SUCCESS; } }
stat() is POSIX 1003.1; stat64() is Large-file support
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | No |
Signal handler | Yes |
Thread | Yes |
errno, fstat(), fstat64(), lstat()