TRUE(1) General Commands Manual TRUE(1)NAME
true, false - provide truth values
True and false are usually used in a Bourne shell script. They test for the appropriate status "true" or "false" before running (or fail-
ing to run) a list of commands.
SEE ALSO csh(1), sh(1), false(1)DIAGNOSTICS
True has exit status zero.
7th Edition April 29, 1985 TRUE(1)
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TEST(1) General Commands Manual TEST(1)NAME
test - condition evaluation utility
The test 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, test also returns 1 (false).
All operators and flags are separate arguments to the test utility.
The following primaries are used to construct expression:
True if file exists and is a block special file.
True if file exists and is a character special file.
True if file exists and is a directory.
True if file exists (regardless of type).
True if file exists and is a regular file.
True if file exists and its set group ID flag is set.
True if file exists and is a symbolic link.
True if the length of string is nonzero.
True if file is a named pipe
True if file exists and is readable.
True if file exists and has a size greater than zero.
True if the file whose file descriptor number is file_descriptor (default 1) is open and is associated with a terminal.
True if file exists and its set user ID flag is set.
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.
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.
True if the length of string is zero.
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.
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 .
These primaries can be combined with the following operators:
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.
True if expression is true.
-a operator has higher precedence than the -o operator.
The test grammar is inherently ambiguous. In order to assure a degree of consistency, the cases described in the IEEE Std 1003.2
("POSIX"), 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.
The test utility exits with one of the following values:
0 expression evaluated to true.
1 expression evaluated to false or expression was missing.
>1 An error occurred.
Named pipes are not implemented in 2.11BSD.
The test function is expected to be IEEE Std 1003.2 ("POSIX") compatible.
7th Edition March 13, 1995 TEST(1)