File Types
/ Usr / include / bits / stat.h
/ * Encoding of the file mode .* /
/ * Take place Acer, 000 001111 000000000000 * /
# Define __S_IFMT 0170000 / * These bits determine file type .* /
/ * 7 kinds of file types-* /
/ * File types .* /
# Define __S_IFDIR 0040000 / * Directory * /
# Define __S_IFCHR 0020000 / * Character device * /
# Define __S_IFBLK 0060000 / * Block device * /
# Define __S_IFREG 0100000 / * Regular file * /
# Define __S_IFIFO 0010000 / * FIFO * /
# Define __S_IFLNK 0120000 / * Symbolic link * /
# Define __S_IFSOCK 0140000 / * Socket * /
16 bits. Designed to save inode corresponding to the mode of the document.
Fifo 000 000001 000000000000 1
Character device 000 000010 000000000000 2
Directory 000 000100 000000000000 4
Block device 000 000110 000000000000 6
Regular file 000 001000 000000000000 8
Symbolic link 000 001010 000000000000 10
Socket 000 001100 000000000000 12
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/ Usr / include / sys / stat.h
# Include <bits/stat.h> / * Hung-that is, from the document * /
/ * 7 kinds of file types-test * /
/ * Test macros for file types * /
# Define __S_ISTYPE (mode, the mask) (((mode) & __S_IFMT) == (mask))
# Define S_ISDIR (mode) __S_ISTYPE ((mode), __S_IFDIR)
# Define S_ISCHR (mode) __S_ISTYPE ((mode), __S_IFCHR)
# Define S_ISBLK (mode) __S_ISTYPE ((mode), __S_IFBLK)
# Define S_ISREG (mode) __S_ISTYPE ((mode), __S_IFREG)
# Ifdef __S_IFIFO
# Define S_ISFIFO (mode) __S_ISTYPE ((mode), __S_IFIFO)
# Endif
# Ifdef __S_IFLNK
# Define S_ISLNK (mode) __S_ISTYPE ((mode), __S_IFLNK)
# Endif
# If defined __USE_BSD & &! Defined __S_IFLNK
# Define S_ISLNK (mode) 0
# Endif
# If (defined __USE_BSD | | defined __USE_UNIX98) /
& & Defined __S_IFSOCK
# Define S_ISSOCK (mode) __S_ISTYPE ((mode), __S_IFSOCK)
# Endif
All seven tests-coupled with the corresponding file types are attributable to the macro-__S_ISTYPE (mode, the mask)
The macro mode of operation is to take place and Acer __ S_IFMT conduct operations to remove mode section 12 to section 15, with the corresponding type of file-mask to compare results is a bool value.
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Use test macros to test a file's type, for example:
File "dir" is a directory. First we get its information via any of the stat functions.
S_ISDIR (buf.st_mode) / * struct stat buf * /
__S_ISTYPE ((Buf.st_mode), __S_IFDIR) / * the corresponding file types-* /
((Buf.st_mode) & 000 001111 000000000000) == (000 000100 000000000000)
/ * Take place Acer * /
And computing, shielding other place, mainly extraction buf.st_mode section 12 to section 15, and the corresponding value of the type of document comparison.
Mode_t is unsigned 32 bits
