[ Previous |
Next |
Contents |
Glossary |
Home |
Search ]
AIX Version 4.3 Commands Reference, Volume 5
test Command
Purpose
Evaluates conditional expressions.
test Expression
OR
[ Expression ]
Description
The test command evaluates the Expression parameter, and if the expression value is True, returns a zero (True) exit value. Otherwise, the test command returns a nonzero (False) exit value. The test command also returns a nonzero exit value if there are no parameters.
Notes:
- In the second form of the command, the [ ] (brackets) must be surrounded by blank spaces.
- You must test explicitly for file names in the C shell. File-name substitution (globbing) causes the shell script to exit.
Functions and operators are treated as separate parameters by the test command. The Expression parameter refers to a statement that is checked for a true or false condition. The following functions are used to construct this parameter:
-b FileName |
Returns a True exit value if the specified FileName exists and is a block special file. |
-c FileName |
Returns a True exit value if the specified FileName exists and is a character special file. |
-d FileName |
Returns a True exit value if the specified FileName exists and is a directory. |
-e FileName |
Returns a True exit value if the specified FileName exists. |
-f FileName |
Returns a True exit value if the specified FileName exists and is a regular file. |
-g FileName |
Returns a True exit value if the specified FileName exists and its Set Group ID bit is set. |
-h FileName |
Returns a True exit value if the specified FileName exists and is a symbolic link. |
-k FileName |
Returns a True exit value if the specified FileName exists and its sticky bit is set. |
-L FileName |
Returns a True exit value if the specified FileName exists and is a symbolic link. |
-n String1 |
Returns a True exit value if the length of the String1 variable is nonzero. |
-p FileName |
Returns a True exit value if the specified FileName exists and is a named pipe (FIFO). |
-r FileName |
Returns a True exit value if the specified FileName exists and is readable by the current process. |
-s FileName |
Returns a True exit value if the specified FileName exists and has a size greater than 0. |
-t FileDescriptor |
Returns a True exit value if the file with a file descriptor number of FileDescriptor is open and associated with a terminal. |
-u FileName |
Returns a True exit value if the specified FileName exists and its Set User ID bit is set. |
-w FileName |
Returns a True exit value if the specified FileName exists and the write flag is on. However, the FileName will not be writable on a read-only file system even if test indicates true. |
-x FileName |
Returns a True exit value if the specified FileName exists and the execute flag is on. If the specified file exists and is a directory, the True exit value indicates that the current process has permission to search in the directory. |
-z String1 |
Returns a True exit value if the length of the String1 variable is 0 (zero). |
String1= String2 |
Returns a True exit value if the String1 and String2 variables are identical. |
String1!=String2 |
Returns a True exit value if the String1 and String2 variables are not identical. |
String1 |
Returns a True exit value if the String1 variable is not a null string. |
Integer1 -eq Integer2 |
Returns a True exit value if the Integer1 and Integer2 variables are algebraically equal. Any of the comparisons -ne, -gt, -ge, -lt, and -le can be used in place of -eq. |
These functions can be combined with the following operators:
! |
Unary negation operator |
-a |
Binary AND operator |
-o |
Binary OR operator ( that is, the -a operator has higher precedence than the -o operator) |
\(Expression\) |
Parentheses for grouping |
Exit Status
This command returns the following exit values:
0 |
The Expression parameter is true. |
1 |
The Expression parameter is false or missing. |
>1 |
An error occurred. |
Examples
- To test whether a file exists and is not empty, enter:
if test ! -s "$1"
then
echo $1 does not exist or is empty.
fi
If the file specified by the first positional parameter to the shell procedure, $1
, does not exist, the test command displays an error message. If $1
exists and has a size greater than 0, the test command displays nothing.
Note: There must be a space between the -s function and the file name.
The quotation marks around $1
ensure that the test works properly even if the value of $1
is a null string. If the quotation marks are omitted and $1
is the empty string, the test command displays the error message test: argument expected.
- To do a complex comparison, enter:
if [ $# -lt 2 -o ! -e "$1" ]
then
exit
fi
If the shell procedure is given fewer than two positional parameters or the file specified by $1
does not exist, then the shell procedure exits. The special shell variable $#
represents the number of positional parameters entered on the command line that starts this shell procedure.
The "Shells Overview" in AIX Version 4.3 System User's Guide: Operating System and Devices describes shells in general, defines terms that are helpful in understanding shells, and describes the more useful shell functions.
File
/usr/bin/test |
Contains the test command. |
Related Information
The bsh command, csh command, find command, ksh command, sh command.
Shells Overview in AIX Version 4.3 System User's Guide: Operating System and Devices.
[ Previous |
Next |
Contents |
Glossary |
Home |
Search ]