Programming :: Getting A Comparison Operator To Work?
Feb 8, 2010
I'm very new at Bash scripting and have a bone head issue that I'm trying (and failing) to resolve. I cannot get this one IF statement to work, it seems the comparison operator does not think the resulting number from the $b*$c+$b operation is an integer even though it is a number. Below is a small proof of concept script with the bit I'm having trouble with.
Code:
#! /bin/bash
a=800
b=700
c=.15
if [ "$a" -le "$(echo "($b*$c+$b)"|bc)" ]
[Code]...
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May 10, 2011
I know it is wrong to use the "==" operator to compare the equality of two floating point numbers. Logically it would seem that if the "==" operator is not usable for floating point comparison, then the "<=" operator would also not be usable. Is this true? The lack of google search results on this topic made me think that it must be true. If that is true, then is it true that the only way to compare floats with <= or >= is with something like the code below? Code: bool smaller_than_or_equal(float a, float b) {
if ( fabs(a-b) < EPSILON){return true;}
else if (a < b) {return true;}
else {return false;}
} I think this is a general question, but if specifics are necessary, I am using the C++ language to code at the moment.
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Nov 23, 2010
I would like to compare the nmlookup result of IP's stored in the file ips with a list of PC names stored in the file pcs.
Code:
for line in `cat "ips"`
do
[code]....
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Apr 18, 2011
I'm having a bit of trouble getting the OR operator to work.This is the code that I have:
global.php:
Code:
$vars["admin link"] = "<a href='/path/to/admin.php'>Admin</a>";
$vars["admin ip"] = "xxx.xxx.xxx.xx1";
$vars["admin ip2"] = "xxx.xxx.xxx.xx2";
[Code]...
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Apr 16, 2011
I'm having a bit of an issue using overloaded operators in an already overloaded operator. In my following code, I have overloaded the && operator to compare two Course objects. The operator in turn goes to a function which calls other overloaded operators to compare private object variables of that object to compare them.
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Jun 29, 2010
how do I get this regular expression to work in an if/else statement? This is just a little script for learning BASH. don't be too harsh.
This script will test if a certain number of files with 1-4 in their filename exist and print their filename. An error message will be printed if not.
#
for i in `ls file[1-9]`
do
if [[ "$i" == *1-4 ]] ; then
echo "This file, $i, ends in a number between 1-4"
else
echo "Error, this file, $i, does not end with a number between 1-4"
fi
done
I get this error. ./file_test.sh: 13: [[: not found
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May 1, 2010
I have a binary value which I receive from a controller. Say this binary value is 42. Just plain hex 42. If you would look at that byte in a debugger you would see 42.Now this value hold 8 bits each indicating a high or a low output. So 0x42 = 01000010b. Which means bits 1 and 6 are '1'.When I would want to find out which bits are set and which are not in a language like C, I simply do:
Code:
mask = 0x80;
if (binval & mask) {...}
etc..
However I am programming in TCL, and I try to do:
Code:
set mask 0x80
if { [expr ($binval & $mask) > 0] } {...}
etc...
this fails. At the moment the expr is executed, $binval is evaluated and substituted so the expression I am evaluating is
Code:
set mask 0x80
if { [expr ('B' & '0x80') > 0] } {...}
etc...
Eventually I got it working by converting the $binval into a '0x42' string value, like this:
Code:
binary scan $binval c byte
set byte [format "0x%0x" $byte]
set mask 0x80
if { [expr ($byte & $mask) > 0] } {...}
etc...[
Then the expression yields what I want. But this seems so stupid and clumsy. Isn't there a better way where I can compare two binary values without conversions?
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Jul 13, 2011
I have a simple program from book C++ cookbook, page 291, 8.3, Using Constructors and Destructors to manage resources (or RAII), but it can not get compiled in my g++
------------------------------------------------------------------------------------------------
// Example 8-3. Using constructors and destructors
#include <iostream>
#include <string>
using namespace std;
[code]....
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Jul 6, 2010
I'm trying to write a simple program that lists a menu and then asks you for your decision, and you can answer with a number or the name. However, I don't know how to add the second options (name).
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Sep 1, 2014
Is there a way to achieve the following with the square bracket operator?I have a class:
Code: Select allclass A
{
public:
void SetValue(int index, Item* B);
private:
int m_iCount;
ItemCollection Item_Collection;
[code]....
The probelm is that I am not just blindly assigning whatever given on the right hand side to the returned value from operator [], I need to verify it's not NULL, and it is not already there in the Item_Collection, and I also need to increase the count.
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Jan 4, 2010
I am trying to learn C++.I implemented a simple archive program, and I am in a situation in which the user is prompted by a menu to make a choice.So I have some cout instruction to illustrate the possible choices and then
int choice;
cin>>choice;
and everything works fine.I introduced this code in a "while" loop that checks wether the choice made by the user is valid or not:
bool check=true;
int choice;
while(check)
{
cin>>choice;
if(the choice is valid) {...;check=false}
else cout<<"please make an other choice"
}
What is happening is that if by mistake the user introduces a character in place of a number, the loop repeats indefinitely because the program, when it get to the "cin" instruction, does not pauses to wait for a new input.
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Apr 25, 2010
Can one of you point me towards a comprehensive print function tutorial in perl? I was under the impression that everything within quotes will get interpolated - but I am running into exceptions where it is not desirable to run some varaibles under quotes.
ordinal.pl
1 #!/usr/bin/perl
2 $idx = 1;
3 foreach $letter (a..z) {
4 print "Letter #",$idx++," is: $letter
";
5 #print "Letter # $idx++ is: $letter
[Code]...
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Jun 12, 2010
I've been reading and googling, etc. I've seen some things, but not a definite explanation of this. What is the appropriate way to mimic a C ternary operator using Python? Isn't there an exact proper way to do it? Any difference for using lambda functions? I'm sorry, but I've been searching and it's ambiguous to me how this should be handled. I would appreciate a person's help on this. I came up with this link, but I'm wondering if I'm missing something.[URL]...
So, is that it? In Dive Into Python, it's using the and-or trick. Well, if the above post is the full explanation,
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Jun 27, 2010
how to overload the subscript operator ([]) for a list class?
Code:
template <typename T>
class list
{
public:
struct node
[Code]...
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Oct 10, 2010
my issue is that the when i put in the correct input its going into the loop like i put in incorrect input and wont break out of the loop even with the correct input entered
Code:
import java.util.*;
import javax.swing.*;
[code]...
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Mar 27, 2010
I have tryed out this operator on program:
Code:
#include <iostream.h>
#include <iomanip.h>
#include <fstream.h>
ofstream myfile;
[code]...
which definitly is not the same number. I guess somewhere in the convertion from double to char* ("<<") something is not right and what can i do to save these double numbers in an accurate manner in a file?
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Mar 23, 2011
I need to be able to compare a file date with system date and delete files older than 30 days.
the file name is basically
error_log.03222011
of course the extension is the date the file was created.
Oh and before i get hammered I looked everywhere but am unable to make sense of what I found.
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Jun 1, 2010
I have a bash script that is tracking ERROR connections (running in a cron every 15 minutes), sometimes the errors are true and are not connecting. But most of the time, the disconnects/reconnects are between 30 seconds are sending out false positives. I am looking for a time comparison code to pick out the 30 second disconnects and know that this is and "ok" error. Here is a section of the log with timestamps, errors, etc.
Tue 2010-06-01 22:01:30 ERROR [DataBufferSendService] 172.31.0.1:8016 caught exception: [NetworkAPI] Exception: [SocketStream] socket error
Tue 2010-06-01 22:01:32 ERROR [DataBufferSendService] 172.31.0.2:8016 caught exception: [NetworkAPI] Exception: [SocketStream] socket error
Tue 2010-06-01 22:02:00 INFO [Client] 172.31.0.1:8016 connecting to 172.31.0.1 on port 8016
Tue 2010-06-01 22:02:02 INFO [Client] 172.31.0.2:8016 connecting to 172.31.0.2 on port 8016
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May 6, 2009
I am fairly new to linux still and I'm currently trying to write a shell script (which I have never done) that is supposed to run the xrestop(like top) program. What I want to do is execute the program and check the identifier column to see if a certain program is running. If it is running I want to strip the data from that row of the terminal say every 5 seconds or so and put it in a text file. Is this going to be a complicated thing?
Heres a list of the columns when you run xrestop program res-base Wins GCs Fnts Pxms Misc PxmMem Other Total PID Identifier.
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Sep 26, 2010
does the assignment operator copy all the members also for structures containing STL objects strings,vectors,vectors of vectors...)? I did try it on my platform,and it works that way (copying all the fields),but i was wondering if it is a standard behavior or not.
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Mar 1, 2010
I need to write a shell script which can compare two files(text files) character wise. eg. underscore is space.
------FILE 1---------------
A_B_C
D_E_F
G_H_I
[code].....
Actual problem: I need to write a shell script which can give me difference character by character not by line (using comm)
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Jan 22, 2010
This one is driving me crazy.
My .bashrc is set as:
if [ -d ~/.bashrc.d ]; then
for file in $(/bin/ls ~/.bashrc.d/); do
[code]....
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May 12, 2010
My compiler won't find <new>. Since it's such a basic function, I'm a bit confused. Is <new> supposed to be in a file of its own? Where do I find it? And if it turns out to be missing on my computer, where can I find a <new> one? Or do you see anything else that I do wrong?
After some trying out, it seems I can't find stuff like iostream or any other basic stuff either. The compiler is prolly looking for them at the wrong place. Does anyone know how I change or add paths for the compiler to look in when using the "<>" operator?
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Feb 24, 2010
if anyone knows plz explain this conditional operator timeout ? : MAX SCHEDULE_TIMEOUT
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Feb 9, 2010
I'm looking at a new board that supports both DDR2 800 and DDR2 667. But, the FSB is only 667MHz. My question is: is there a benefit of using the DDR2 800 on the 667 FSB? That is, can the DDR2 800 be fully utilized on this system? What are pros and cons of such? Does the added benefit outweigh the additional cost of the RAM?
Note: I'm not looking to overclock at all, and this is not going to be used for 3D apps (games or video editing).
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Jan 29, 2010
i am not able to understand the appropriate thing to put in the google search...
Is there a way to use the ?: operator for if-else decision in a shell script?
edit: the 'question mark - colon' operator (just editing so that its searchable by someone in need :-P)
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Oct 14, 2010
$dec93 = 93;
$ser = SERVO;
$lbit = uc(sprintf("%02x
", $dec93));
if($lbit == 5D){
print DATA "Byte11: $fbits11=$bstr11 Bits:[95-88] $ser
";
}else{
sleep(1);
}
Why do I get this error? Bareword found where operator expected at C:Perl ScriptsLbits.pl line 64, near "5D" (Missing operator before D?)
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Nov 25, 2010
Does anybody here use Tyan System Operator (TSO) in ubuntu sever? It seems that the packages are for redhat only
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Oct 3, 2010
I would like to check if the 3rd character from the end of a string is a d or p using awk and the field seperator would not help for this problem, i.e.
Code:
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Oct 26, 2010
I have been spending several days getting wxwidgets to work in code::blocks ide on several different platforms. Now I am down to one instance that I can't figure out. I have wxwidgets working in Fedora 13 x64, but cannot get it to work in a Fedora 13 x32 version. Actually, wxwidgets seem to be installed OK, but I run into compiler errors when I try to compile the default wxhello project. I get quite a few messages, in different header files, of this type:
/usr/include/assert.h:39:42: error: missing binary operator before token "("#if defined __cplusplus && __GNUC_PREREQ (2,95) From my friend Google this would seem to be caused by an older version of boost (before 1.37) - see http://bugs.xmms2.xmms.se/view.php?id=2215 ("It is an issue with old versions of boost and gcc4.4 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36453 It is fixed in boost 1.37")
I did a yum info command on both systems for every relevant package I could think of, including gcc(v4.4.4), gcc-c++(4.4.4), libgcc(4.4.4), libstdc++(4.4.4), boost(1.41.0), wxGTK(2.8.11), wxBase(2.8.11). Both systems are fully updated and have the same versions, with the only difference being 32 vs 64 bit. The same headers compile with no errors on the x64 system, but not x32. I have been able to find no other reason for this error than older versions of the preprocessor, yet that is apparently not the case here).
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