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Full Discussion: unary operator expected
Top Forums Shell Programming and Scripting unary operator expected Post 302295013 by Corona688 on Friday 6th of March 2009 10:16:55 AM
Old 03-06-2009
If $j has no value at all, the expression will be invalid because it will vanish entirely, making it look like just [ -j 50 ]. Wrap $j in double-quotes and it won't vanish, becoming [ "" -lt 50 ] , which still isn't altogether sensible -- comparing a blank string to an integer -- but at least has correct syntax.
 

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LEARN ABOUT POSIX

powf

POW(P)							     POSIX Programmer's Manual							    POW(P)

NAME

       pow, powf, powl - power function

SYNOPSIS

       #include <math.h>

       double pow(double x, double y);
       float powf(float x, float y);
       long double powl(long double x, long double y);

DESCRIPTION

       These functions shall compute the value of x raised to the power y, x**y. If x is negative, the application shall ensure that y is an inte-
       ger value.

       An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT)  before  calling  these
       functions.   On	return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error
       has occurred.

RETURN VALUE

       Upon successful completion, these functions shall return the value of x raised to the power y.

       For finite values of x < 0, and finite non-integer values of y, a domain error shall occur and	 either a NaN (if representable),  or	an
       implementation-defined value shall be returned.

       If  the	correct  value would cause overflow, a range error shall occur and pow(), powf(), and powl() shall return +-HUGE_VAL, +-HUGE_VALF,
       and +-HUGE_VALL, respectively, with the same sign as the correct value of the function.

       If the correct value would cause underflow, and is not representable, a range error may occur, and    either 0.0 (if  supported),  or	an
       implementation-defined value shall be returned.

       If x or y is a NaN, a NaN shall be returned (unless specified elsewhere in this description).

       For any value of y (including NaN), if x is +1, 1.0 shall be returned.

       For any value of x (including NaN), if y is +-0, 1.0 shall be returned.

       For any odd integer value of y > 0, if x is +-0, +-0 shall be returned.

       For y > 0 and not an odd integer, if x is +-0, +0 shall be returned.

       If x is -1, and y is +-Inf, 1.0 shall be returned.

       For |x| < 1, if y is -Inf, +Inf shall be returned.

       For |x| > 1, if y is -Inf, +0 shall be returned.

       For |x| < 1, if y is +Inf, +0 shall be returned.

       For |x| > 1, if y is +Inf, +Inf shall be returned.

       For y an odd integer < 0, if x is -Inf, -0 shall be returned.

       For y < 0 and not an odd integer, if x is -Inf, +0 shall be returned.

       For y an odd integer > 0, if x is -Inf, -Inf shall be returned.

       For y > 0 and not an odd integer, if x is -Inf, +Inf shall be returned.

       For y < 0, if x is +Inf, +0 shall be returned.

       For y > 0, if x is +Inf, +Inf shall be returned.

       For  y  an odd integer < 0, if x is +-0, a pole error shall occur and +-HUGE_VAL, +-HUGE_VALF, and +-HUGE_VALL shall be returned for pow(),
       powf(), and powl(), respectively.

       For y < 0 and not an odd integer, if x is +-0, a pole error shall occur and HUGE_VAL, HUGE_VALF, and HUGE_VALL shall be returned for pow(),
       powf(), and powl(), respectively.

       If the correct value would cause underflow, and is representable, a range error may occur and the correct value shall be returned.

ERRORS

       These functions shall fail if:

       Domain Error
	      The value of x is negative and y is a finite non-integer.

       If  the	integer  expression  (math_errhandling	&  MATH_ERRNO)	is  non-zero, then errno shall be set to [EDOM]. If the integer expression
       (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

       Pole Error
	      The value of x is zero and y is negative.

       If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set  to  [ERANGE].  If  the  integer	expression
       (math_errhandling & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.

       Range Error
	      The result overflows.

       If  the	integer  expression  (math_errhandling	&  MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. If the integer expression
       (math_errhandling & MATH_ERREXCEPT) is non-zero, then the overflow floating-point exception shall be raised.

       These functions may fail if:

       Range Error
	      The result underflows.

       If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set  to  [ERANGE].  If  the  integer	expression
       (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       On  error,  the	expressions  (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at
       least one of them must be non-zero.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       exp() , feclearexcept() , fetestexcept() , isnan() , the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of  Error
       Conditions for Mathematical Functions, <math.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical  and	Electronics  Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE
       and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can  be  obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								    POW(P)
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