【标题】：test conditions provided by the shell(摘要)
【关键字】：test,conditions,provided,by,the,shell
【来源】：http://www.cublog.cn/u/12054/showart.php?id=114911

test conditions provided by the shell(摘要)

The tests below are test conditions provided by the shell:

-b file = True if the file exists and is block special file.
-c file = True if the file exists and is character special file.
-d file = True if the file exists and is a directory.
-e file = True if the file exists.
-f file = True if the file exists and is a regular file
-g file = True if the file exists and the set-group-id bit is set.
-k file = True if the files' "sticky" bit is set.
-L file = True if the file exists and is a symbolic link.
-p file = True if the file exists and is a named pipe.
-r file = True if the file exists and is readable.
-s file = True if the file exists and its size is greater than zero.
-s file = True if the file exists and is a socket.
-t fd = True if the file descriptor is opened on a terminal.
-u file = True if the file exists and its set-user-id bit is set.
-w file = True if the file exists and is writable.
-x file = True if the file exists and is executable.
-O file = True if the file exists and is owned by the effective user id.
-G file = True if the file exists and is owned by the effective group id.
file1 –nt file2 = True if file1 is newer, by 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.
-z string = True if the length of the string is 0.
-n string = True if the length of the string is non-zero.
string1 = string2 = True if the strings are equal.
string1 != string2 = True if the strings are not equal.
!expr = True if the expr evaluates to false.
expr1 –a expr2 = True if both expr1 and expr2 are true.
expr1 –o expr2 = True is either expr1 or expr2 is true.