The
utility evaluates the expression and, if it evaluates
to true, returns a zero (true) exit status; otherwise
it returns 1 (false).
If there is no expression,
also
returns 1 (false).
All operators and flags are separate arguments to the
utility.
The following primaries are used to construct expression:
-b file
True if
file
exists and is a block special
file.
-c file
True if
file
exists and is a character
special file.
-d file
True if
file
exists and is a directory.
-e file
True if
file
exists (regardless of type).
-f file
True if
file
exists and is a regular file.
-g file
True if
file
exists and its set group ID flag
is set.
-h file
True if
file
exists and is a symbolic link.
This operator is retained for compatibility with previous versions of
this program.
Do not rely on its existence; use
-L
instead.
-k file
True if
file
exists and its sticky bit is set.
-n string
True if the length of
string
is nonzero.
-p file
True if
file
is a named pipe
(FIFO
)
-r file
True if
file
exists and is readable.
-s file
True if
file
exists and has a size greater
than zero.
-t file_descriptor
True if the file whose file descriptor number
is
file_descriptor
is open and is associated with a terminal.
-u file
True if
file
exists and its set user ID flag
is set.
-w file
True if
file
exists and is writable.
True
indicates only that the write flag is on.
The file is not writable on a read-only file
system even if this test indicates true.
-x file
True if
file
exists and is executable.
True
indicates only that the execute flag is on.
If
file
is a directory, true indicates that
file
can be searched.
-z string
True if the length of
string
is zero.
-L file
True if
file
exists and is a symbolic link.
-O file
True if
file
exists and its owner matches the effective user id of this process.
-G file
True if
file
exists and its group matches the effective group id of this process.
-S file
True if
file
exists and is a socket.
file1 -nt file2
True if
file1
exists and is newer than
file2
file1 -ot file2
True if
file1
exists and is older than
file2
file1 -ef file2
True if
file1
and
file2
exist and refer to the same file.
string
True if
string
is not the null
string.
s1 = s2
True if the strings
s1
and
s2
are identical.
s1 != s2
True if the strings
s1
and
s2
are not identical.
s1 < s2
True if string
s1
comes before
s2
based on the binary value of their characters.
s1 > s2
True if string
s1
comes after
s2
based on the binary value of their characters.
n1 -eq n2
True if the integers
n1
and
n2
are algebraically
equal.
n1 -ne n2
True if the integers
n1
and
n2
are not
algebraically equal.
n1 -gt n2
True if the integer
n1
is algebraically
greater than the integer
n2
n1 -ge n2
True if the integer
n1
is algebraically
greater than or equal to the integer
n2
n1 -lt n2
True if the integer
n1
is algebraically less
than the integer
n2
n1 -le n2
True if the integer
n1
is algebraically less
than or equal to the integer
n2
If
file
is a symbolic link,
will fully dereference it and then evaluate the expression
against the file referenced, except for the
-h
and
-L
primaries.
These primaries can be combined with the following operators:
! expression
True if
expression
is false.
expression1 -a expression2
True if both
expression1
and
expression2
are true.
expression1 -o expression2
True if either
expression1
or
expression2
are true.
( expression )
True if expression is true.
The
-a
operator has higher precedence than the
-o
operator.
Some shells may provide a builtin
command which is similar or identical to this utility.
Consult the
builtin(1)
manual page.
GRAMMAR AMBIGUITY
The
grammar is inherently ambiguous.
In order to assure a degree of consistency,
the cases described in the
St -p1003.2 ,
section D11.2/4.62.4, standard
are evaluated consistently according to the rules specified in the
standards document.
All other cases are subject to the ambiguity in the
command semantics.
RETURN VALUES
The
utility exits with one of the following values:
0
expression evaluated to true.
1
expression evaluated to false or expression was
missing.
The
utility implements a superset of the
St -p1003.2
specification.
BUGS
Both sides are always evaluated in
-a
and
-o
unlike in the logical operators of
sh(1).
For instance, the writable status of
file
will be tested by the following command even though the former expression
indicated false, which results in a gratuitous access to the file system:
