Formats

Format strings are similar to printf(3) formats in that they start with %, are then followed by a sequence of formatting characters, and end in a character that selects the field of the struct stat which is to be formatted. If the % is immediately followed by one of n, t, %, or @, then a newline character, a tab character, a percent character, or the current file number is printed, otherwise the string is examined for the following:

Any of the following optional flags:

#

Selects an alternate output form for octal and hexadecimal output. Non-zero octal output will have a leading zero, and non-zero hexadecimal output will have “ 0x” prepended to it.

+

Asserts that a sign indicating whether a number is positive or negative should always be printed. Non-negative numbers are not usually printed with a sign.

-

Aligns string output to the left of the field, instead of to the right.

0

Sets the fill character for left padding to the ‘ 0’ character, instead of a space.

space

Reserves a space at the front of non-negative signed output fields. A ‘ +’ overrides a space if both are used.

Then the following fields:

size

An optional decimal digit string specifying the minimum field width.

prec

An optional precision composed of a decimal point ‘ .’ and a decimal digit string that indicates the maximum string length, the number of digits to appear after the decimal point in floating point output, or the minimum number of digits to appear in numeric output.

fmt

An optional output format specifier which is one of D, O, U, X, F, or S. These represent signed decimal output, octal output, unsigned decimal output, hexadecimal output, floating point output, and string output, respectively. Some output formats do not apply to all fields. Floating point output only applies to timespec fields (the a, m, and c fields).

The special output specifier S may be used to indicate that the output, if applicable, should be in string format. May be used in combination with:

amc

Display date in strftime(3) format.

dr

Display actual device name.

f

Display the flags of file as in ls -lTdo.

gu

Display group or user name.

p

Display the mode of file as in ls -lTd.

N

Displays the name of file.

T

Displays the type of file.

Y

Insert a “ -> ” into the output. Note that the default output format for Y is a string, but if specified explicitly, these four characters are prepended.

sub

An optional sub field specifier (high, middle, low). Only applies to the p, d, r, and T output formats. It can be one of the following:

H

“High”— specifies the major number for devices from r or d, the “user” bits for permissions from the string form of p, the file “type” bits from the numeric forms of p, and the long output form of T.

L

“Low”— specifies the minor number for devices from r or d, the “other” bits for permissions from the string form of p, the “user”, “group”, and “other” bits from the numeric forms of p, and the ls -F style output character for file type when used with T (the use of L for this is optional).

M

“Middle”— specifies the “group” bits for permissions from the string output form of p, or the “suid”, “sgid”, and “sticky” bits for the numeric forms of p.

datum

A required field specifier, being one of the following:

d

Device upon which file resides ( st_dev).

i

file's inode number ( st_ino).

p

File type and permissions ( st_mode).

l

Number of hard links to file ( st_nlink).

u, g

User ID and group ID of file's owner ( st_uid, st_gid).

r

Device number for character and block device special files ( st_rdev).

a, m, c, B

The time file was last accessed or modified, or when the inode was last changed, or the birth time of the inode ( st_atime, st_mtime, st_ctime, st_birthtime).

z

The size of file in bytes ( st_size).

b

Number of blocks allocated for file ( st_blocks).

k

Optimal file system I/O operation block size ( st_blksize).

f

User defined flags for file.

v

Inode generation number ( st_gen).

The following five field specifiers are not drawn directly from the data in struct stat, but are:

N

The name of the file.

R

The absolute pathname corresponding to the file.

T

The file type, either as in ls -F or in a more descriptive form if the sub field specifier H is given.

Y

The target of a symbolic link.

Z

Expands to “major,minor” from the rdev field for character or block special devices and gives size output for all others.

Only the % and the field specifier are required. Most field specifiers default to U as an output form, with the exception of p which defaults to O; a, m, and c which default to D; and Y, T, and N which default to S.