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expr help - managing strings
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test(1sh5) test(1sh5) Name test - condition evaluation command Syntax test expr [ expr ] Description The command evaluates the expression expr. If the value of expr is true, the command returns a zero exit status; otherwise, it returns a nonzero exit status. The command also returns a nonzero exit status if no arguments are specified. The following primitives are used to construct expr: -r file True if file exists and is readable. -w file True if file exists and is writable. -x file True if file exists and is executable. -f file True if file exists and is a regular file. -d file True if file exists and is a directory. -c file True if file exists and is a character special file. -b file True if file exists and is a block special file. -p file True if file exists and is a named pipe (fifo). -u file True if file exists and its set-user-ID bit is set. -g file True if file exists and its set-group-ID bit is set. -k file True if file exists and its sticky bit is set. -s file True if 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 non-zero. s1 = s2 True if strings s1 and s2 are identical. s1 != s2 True if strings s1 and s2 are not identical. 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, and -le may be used in place of -eq. These primitives can be combined with the following operators: ! unary negation operator. -a binary and operator. -o binary or operator (-a has higher precedence than -o). ( expr ) parentheses for grouping. Note that all the operators and flags are separate arguments to the command. Note also that parentheses are meaningful to the Shell and must be escaped. In the form of the command that uses square brackets ([]), instead of the word test, the brackets must be delimited by blanks. See Also find(1), sh5(1), test(1) test(1sh5)
