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Full Discussion: Unsigned to signed, error?...
Operating Systems OS X (Apple) Unsigned to signed, error?... Post 302904967 by wisecracker on Sunday 8th of June 2014 03:10:54 PM
Old 06-08-2014
Unsigned to signed, error?...
Hi guys...
Macbook Pro, 13", circa August 2012, OSX 10.7.5, default bash terminal.

I require the capability to convert +32767 to -32768 into signed hex words...
The example piece code below works perfectly except...
Code:
#/bin/bash
# sign.sh
# Unsign to sign...
while true
do
	# I have used $(( ~n )), where n is a positive integer too.
	# Test piece only hence no error checking at all.
	read -p "Enter negative number -1 to -32768:- " num
	if [ $num -le -1 ]
	then
		printf "$[ ( $num + 65536 ) ]\n"
	else
		printf "Zero or positive value entered, $num.\n"
	fi
	# Why a 64 bit _hex_ value here?
	hex=$(printf "%04X\n" $num)
	printf "$hex\n"
	# I have to use this to correct.
	if [ ${#hex} -gt 4 ]
	then
		hex="${hex:$[ ( ${#hex} - 4 ) ]:4}"
	fi
	printf "$hex\n"
done

Results:-
Code:
Last login: Sun Jun  8 19:52:33 on ttys000
AMIGA:barrywalker~> ./sign.sh
Enter negative number -1 to -32768:- 0
Zero or positive value entered, 0.
0000
0000
Enter negative number -1 to -32768:- 1
Zero or positive value entered, 1.
0001
0001
Enter negative number -1 to -32768:- -1
65535
FFFFFFFFFFFFFFFF
FFFF
Enter negative number -1 to -32768:- 32767
Zero or positive value entered, 32767.
7FFF
7FFF
Enter negative number -1 to -32768:- -32768
32768
FFFFFFFFFFFF8000
8000
Enter negative number -1 to -32768:- ^CAMIGA:barrywalker~> 
AMIGA:barrywalker~> _

My question is this:-
Why does the line hex=$(printf "%04X\n" $num) not truncate the hex
string to 4 characters?
I have tried, %04X, %02X and %X along with $num and "$num" but I still have to use the extra code to correct to 4 hex characters.

TIA...
 

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LEARN ABOUT PLAN9

prime

PRIME(1SSL)							      OpenSSL							       PRIME(1SSL)

NAME

       openssl-prime, prime - compute prime numbers

SYNOPSIS

       openssl prime [-help] [-hex] [-generate] [-bits] [-safe] [-checks] [number...]

DESCRIPTION

       The prime command checks if the specified numbers are prime.

       If no numbers are given on the command line, the -generate flag should be used to generate primes according to the requirements specified
       by the rest of the flags.

OPTIONS

       [-help]
	   Display an option summary.

       [-hex]
	   Generate hex output.

       [-generate]
	   Generate a prime number.

       [-bits num]
	   Generate a prime with num bits.

       [-safe]
	   When used with -generate, generates a "safe" prime. If the number generated is n, then check that (n-1)/2 is also prime.

       [-checks num]
	   Perform the checks num times to see that the generated number is prime.  The default is 20.

COPYRIGHT

       Copyright 2017 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use this file except in compliance with the License.  You can obtain a
       copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

1.1.1a								    2018-12-18							       PRIME(1SSL)
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