Conditional expressions
Conditional expressions are used by bracketed expressions
and the test builtin.
Conditional expressions are often used to examine the status of a file.
-a file
- True if file exists.
-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.
-f file
- True if file exists and is a regular file.
-g file
- True if file exists and its set-group-id bit
is set.
-h file
- True if file exists and is a symbolic link.
-k file
- True if file exists and its "sticky" bit is
set.
-p file
- True if file exists and 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 fd
- True if file descriptor fd is open and refers
to a terminal.
-u file
- True if file exists and its set-user-id bit
is set.
-w file
- True if file exists and is writable.
-x file
- True if file exists and is executable.
-O file
- True if file exists and is owned by the effective
user id.
-G file
- True if file exists and is owned by the effective
group id.
-L file
- True if file exists and is a symbolic link.
-S file
- True if file exists and is a socket.
-N file
- True if file exists and has been modified
since it was last read.
file1 -nt file2
- True if file1 is newer (according to modification
date) than file2.
file1 -ot file2
- True if file1 is older than file2.
file1 -ef file2
- True if file1 and file2 have the
same device and inode numbers.
-o optname
- True if shell option optname is enabled. The
list of options appears in the description of the `-o' option
to
set.
-z string
- True if the length of string is zero.
-n string
-
-
- True if the length of string is non-zero.
string1 == string2
- True if the strings are equal. `=' may be
used in place of `=='.
string1 != string2
- True if the strings are not equal.
string1 < string2
- True if string1 sorts before string2
lexicographically in the current locale.
string1 > string2
- True if string1 sorts after string2
lexicographically in the current locale.
arg1 OP arg2
OP is one of `-eq', `-ne',
`-lt', `-le', `-gt', or `-ge'.
These arithmetic binary operators return true if arg1 is equal
to, not equal to, less than, less than or equal to, greater than, or greater
than or equal to arg2, respectively. Arg1 and arg2
may be positive or negative integers.
If the file argument to one of the primaries is one of
`/dev/stdin'
`/dev/stdout'
`/dev/stderr'
file descriptor 0, 1, or 2, respectively, is checked.
If the file argument to one of the primaries is of the form `/dev/fd/N',
then file descriptor N is checked.
