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Error Checking Input C


Reply ↓ Chuck March 10, 2013 at 5:03 pm Revised working code. For example, $ ./a.out Enter a number (0-9) :15 Damn you! $ ./a.out Enter a number (0-9) :5 Good Enter a number (0-9) :3 Good Enter a number (0-9) :-1 Damn Reply ↓ Jack Post authorFebruary 20, 2014 at 11:28 am Hi Arturo, That's weird, the loop should pull the first value and garbage collect the return. For example, $ ./a.out Enter a number (0-9) :^[[A Damn you! $ Why is this odd behavior? weblink

One kind of error the user can make is to enter a negative number. Code: #include #include #include using namespace std; //................................ // defines constants //................................ #define EUR 1.07892 #define BRI 1.57719 #define JAP 0.00835838 #define AUS 0.601142 #define IRA 3.21647 int It may also need to check that the values are within acceptable limits. If you enter something with leading digits (like "12efg"), scanf will read, convert, and assign the leading "12", leaving the "efg" in the input stream. http://stackoverflow.com/questions/8817098/how-validate-user-input-when-the-expected-value-is-of-type-int-and-the-entered-v

Error Checking Input C

If processing of a directive fails, no further input is read, and scanf() returns. If it's not a valid double, cin will enter a fail state, so cin will evaluate to false. The safe way to check for digit values is to use the isdigit library function (there are also the isodigit and isxdigit functions for checking octal and hexadecimal digits, respectively), such This has been a long time struggle for me in college now I never have to worry about this annoying problem again!

Also I don't know why you assign something to status with the scanf when you should just &status for assignment.
int main(void){
// input user input and strerror() The C programming language provides perror() and strerror() functions which can be used to display the text message associated with errno. Luckily, I was able to parse through the extra characters one-by-one and get something working. Input Validation Error Types I simply do not want the user to enter in an Alpha character, but I dont want to explicitly limit the range either.

Another solution is to read each character at a time. Error Checking C Drive Analyzing the Program The computational core (the function sum_squares()) of the checking.c program is short, but the input validation support makes it more involved than the examples we have given before. Forum Today's Posts C and C++ FAQ Forum Actions Mark Forums Read Quick Links View Forum Leaders What's New? http://stackoverflow.com/questions/15228388/input-validation-using-scanf My advice -there- would be to always initialise everything so that you don't end up getting weird logic results like you have there.

I don't want to get lung cancer like you do Asking Client for discount on Ticket to amusement park How to avoid contributors from claiming about my LGPL-released software? How To Validate Input In C Programming Using DC voltage instead of AC to supply SMPS more hot questions lang-c about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback For example, the archive search may not work with year values less than 1958 or greater than 2004. Is a minus sign allowed in the front? –eq- Nov 1 '10 at 20:05 You list two conditions and an if statement.

Error Checking C Drive

Exiting...\n"); exit(-1); } quotient = dividend / divisor; fprintf(stderr, "Value of quotient : %d\n", quotient ); exit(0); } When the above code is compiled and executed, it produces the following result Quick Navigation C++ Programming Top Site Areas Settings Private Messages Subscriptions Who's Online Search Forums Forums Home Forums General Programming Boards C++ Programming C Programming C# Programming Game Programming Networking/Device Communication Error Checking Input C Basically it checks if the integer x/x = 1. C Atoi Error Checking The main() function manages the flow, delegating tasks to the other functions.

if(number is an integer) { statement 1 statement 2 } 3. http://megavoid.net/error-checking/error-checking-php-ini.html switch(input) { case 1: { printf ("%0.2lf Euros is equal to %0.2lf US dollars\n\n", currency, EURC); break; } case 2: { printf ("%0.2lf British pounds is equal to %0.2lf US dollars\n\n", Could clouds on aircraft wings produce lightning? share|improve this answer answered Nov 1 '10 at 19:38 abelenky 37k1465119 Sorry, people seem to be raving over this answer, but I expected exactly what you wrote from the Input Validation Error

For this you should rather use parsing and strtol for instance. Reply ↓ Valentine September 21, 2016 at 9:32 pm What does it mean when you say EOF in this line code? The program limits the upper and lower bounds of the range to 1000 and 1000, respectively. http://megavoid.net/error-checking/error-checking-on-hdd.html Let's try to simulate an error condition and try to open a file which does not exist.

If the input string doesn't start with a digit (such as "ab123"), none of the input string will be read, and num will contain whatever value it had before the call C Programming Check If Input Is Integer Search Engine Optimisation provided by DragonByte SEO v2.0.32 (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd. These articles are provided as-is and should be used at your own discretion.

These extra hidden characters are what is messing with your input and spawning the infinite while loop.

If it fails to do so, the function enters the body of the outer while loop. Save your draft before refreshing this page.Submit any pending changes before refreshing this page. Here's a little example for you: Code: #include int main(){ double d; std::cout << "Enter a number > "; std::cin >> d; while (!std::cin){ std::cout << "Not a number! Validate Input C Code: std::cin.ignore(0x7FFFL,'\n'); // Ignore the whole buffer 07-22-2003 #6 Cat View Profile View Forum Posts Registered User Join Date May 2003 Posts 1,619 It was big enough to fit the bill

Get Started with C or C++ C Tutorial C++ Tutorial Get the C++ Book All Tutorials Advanced Search Forum General Programming Boards C++ Programming Error checking user input Getting started with You'd probably like to reject this entire input as invalid. Only problem here is that atoi returns 0 on failure (you can't determine if it's 0 because of failure or because the value is 0). http://megavoid.net/error-checking/error-checking.html Always give the user meaningful feedback Tell the user what you expect to read as input /* example one, a simple continue statement */ #include #include main() { int

Abhishek Singh, Web developerWritten 73w agoThe typical way to accept the integer input is :int a; scanf("%d",&a); However you cannot detect a float with %d as the start of any float I'll check how the strtol function works. Thank you so much. –Gal Nov 1 '10 at 20:15 add a comment| up vote 22 down vote You need to read your input as a string first, then parse the The %i conversion specifier handles decimal, octal, and hexadecimal formats, but you still have the first two problems.

Suppose, for example, that you're writing a program that prompts the user to enter a nonnegative integer. It is set as a global variable and indicates an error occurred during any function call. while (input == 0 || !(input>= 1 && input <= 5)) { cout<<"Select from the following 5 options:\n\n"; cout<<"To convert the Euro to US $, please press 1\n\n"; cout<<"To convert the If it does (as it would with a number), its an integer/double.

I'm not sure how scanf() handles this. Else printf(Please enter a valid integer number)Basically if a user enters a float then he should be made aware that only integers are allowed .Please restrict yourself to C language .I Below is my code for your review. more stack exchange communities company blog Stack Exchange Inbox Reputation and Badges sign up log in tour help Tour Start here for a quick overview of the site Help Center Detailed

Wrong password - number of retries - what's a good number to allow? How can I list two concurrent careers, one full time and one freelance, on a CV? Assume the call scanf("%d", &val); If your input stream looks like {'\n', '\t', ' ', '1', '2', '3', '\n'}, scanf will skip over the leading whitespace characters, read and convert "123", Reply ↓ David February 22, 2016 at 6:50 pm Thank you Jack!

is a legal number. C Programming Handling User Input In C scanf() has problems, in that if a user is expected to type an integer, and types a string instead, often the program bombs. It then stores the integer binary representation of that value in an int variable. int input = 0; double currency = 0; double EURC = 0; double BRIC = 0; double JAPC = 0; double AUSC = 0; double IRAC = 0; //................................. //request user