test(1)
NAME
test − condition command
SYNTAX
test expr
DESCRIPTION
The test command evaluates the expression expr. If its value is true then returns zero exit status, otherwise, a non zero exit status. If there are no arguments, test returns a non-zero exit.
The following primitives are used to construct expr.
−r file True if the file exists and is readable.
−w file True if the file exists and is writable.
−f file True if the file exists and is not a directory.
−d file True if the file exists and is a directory.
−s file True if the file exists and has a size greater than zero.
−t [ fildes ]
True if the open file whose file descriptor number is fildes (1 by default) is associated with a terminal device.
−z s1 True if the length of string s1 is zero.
−n s1 True if the length of the string s1 is nonzero.
s1 = s2 True if the strings s1 and s2 are equal.
s1 != s2 True if the strings s1 and s2 are not equal.
s1 True if s1 is not the null string.
n1 −eq n2
True if the integers n1 and n2 are algebraically equal. Any of the comparisons −ne, −gt, −ge, −lt, or −le may be used in place of −eq.
These primaries may be combined with the following operators:
! Unary negation operator
−a Binary and operator
−o Binary or operator
( expr )
Parentheses for grouping.
Note that −a has higher precedence than −o. Notice that all the operators and flags are separate arguments to test. Notice also that parentheses are meaningful to the Shell and must be escaped.