09-20-2006
(+ sign) Unexpected arithmetic expr script interpretation
In response to Glenn Arndt's response, am I correct in stating that, if I declare a value of num1 and num2 outside of the script, I will find that these values are not automatically accessible from within the script?
I'm guessing that the answer to the last question is yes.
In regards to the script lines you advocate :
#!/bin/bash
num1=$1
num2=$2
num3=`expr $num1 + $num2`
echo $num3
I can see how that works - but am still interested in if the script can access variables written outside of it.
When typing the below into the script, could anyone tell me the significance of the 3rd line? I suppose that this is just a different way of evoking a shell script :
$ num1=1
$ num2=2
$ . lazyadd2
Finally, in regards to gkrishnag, I did try the below :
num1=1
num2=2
num3=`expr {$num1} + {$num2}`
echo $num3
But here's what I get :
$ num3=`expr {$num1} + {num2}`
expr: non-numeric argument
$ echo $num3
That is, what you suggested is not recognised as valid.
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LEARN ABOUT NETBSD
prop_number_unsigned_integer_value
PROP_NUMBER(3) BSD Library Functions Manual PROP_NUMBER(3)
NAME
prop_number, prop_number_create_integer, prop_number_create_unsigned_integer, prop_number_copy, prop_number_size, prop_number_unsigned,
prop_number_integer_value, prop_number_unsigned_integer_value, prop_number_equals, prop_number_equals_integer,
prop_number_equals_unsigned_integer -- numeric value property object
LIBRARY
Property Container Object Library (libprop, -lprop)
SYNOPSIS
#include <prop/proplib.h>
prop_number_t
prop_number_create_integer(int64_t val);
prop_number_t
prop_number_create_unsigned_integer(uint64_t val);
prop_number_t
prop_number_copy(prop_number_t number);
int
prop_number_size(prop_number_t number);
bool
prop_number_unsigned(prop_number_t number);
int64_t
prop_number_integer_value(prop_number_t number);
uint64_t
prop_number_unsigned_integer_value(prop_number_t number);
bool
prop_number_equals(prop_number_t num1, prop_number_t num2);
bool
prop_number_equals_integer(prop_number_t number, int64_t val);
bool
prop_number_equals_unsigned_integer(prop_number_t number, uint64_t val);
DESCRIPTION
The prop_number family of functions operate on a numeric value property object type. Values are either signed or unsigned, and promoted to a
64-bit type (int64_t or uint64_t, respectively).
It is possible to compare number objects that differ in sign. Such comparisons first test to see if each object is within the valid number
range of the other:
o Signed numbers that are greater than or equal to 0 can be compared to unsigned numbers.
o Unsigned numbers that are less than or equal to the largest signed 64-bit value (INT64_MAX) can be compared to signed numbers.
Number objects have a different externalized representation depending on their sign:
o Signed numbers are externalized in base-10 (decimal).
o Unsigned numbers are externalized in base-16 (hexadecimal).
When numbers are internalized, the sign of the resulting number object (and thus its valid range) is determined by a set of rules evaluated
in the following order:
o If the first character of the number is a '-' then the number is signed.
o If the first two characters of the number are '0x' then the number is unsigned.
o If the number value fits into the range of a signed number then the number is signed.
o In all other cases, the number is unsigned.
prop_number_create_integer(int64_t val)
Create a numeric value object with the signed value val. Returns NULL on failure.
prop_number_create_unsigned_integer(uint64_t val)
Create a numeric value object with the unsigned value val. Returns NULL on failure.
prop_number_copy(prop_number_t number)
Copy a numeric value object. If the supplied object isn't a numeric value, NULL is returned.
prop_number_size(prop_number_t number)
Returns 8, 16, 32, or 64, representing the number of bits required to hold the value of the object. If the supplied object isn't a
numeric value, NULL is returned.
prop_number_unsigned(prop_number_t number)
Returns true if the numeric value object has an unsigned value.
prop_number_integer_value(prop_number_t number)
Returns the signed integer value of the numeric value object. If the supplied object isn't a numeric value, zero is returned. Thus,
it is not possible to distinguish between ``not a prop_number_t'' and ``prop_number_t has a value of 0''.
prop_number_unsigned_integer_value(prop_number_t number)
Returns the unsigned integer value of the numeric value object. If the supplied object isn't a numeric value, zero is returned.
Thus, it is not possible to distinguish between ``not a prop_number_t'' and ``prop_number_t has a value of 0''.
prop_number_equals(prop_number_t num1, prop_number_t num2)
Returns true if the two numeric value objects are equivalent. If at least one of the supplied objects isn't a numeric value, false is
returned.
prop_number_equals_integer(prop_number_t number, int64_t val)
Returns true if the object's value is equivalent to the signed value val. If the supplied object isn't a numerical value or if val
exceeds INT64_MAX, false is returned.
prop_number_equals_unsigned_integer(prop_number_t number, uint64_t val)
Returns true if the object's value is equivalent to the unsigned value val. If the supplied object isn't a numerical value or if val
exceeds INT64_MAX, false is returned.
SEE ALSO
prop_array(3), prop_bool(3), prop_data(3), prop_dictionary(3), prop_object(3), prop_string(3), proplib(3)
HISTORY
The proplib property container object library first appeared in NetBSD 4.0.
BSD
January 21, 2008 BSD