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Basic c #17

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62a9846
Update basic.c
Christy538 Oct 2, 2020
72c5866
Merge pull request #1 from Christy538/Christy538-patch-1
Christy538 Oct 2, 2020
6ddaba3
Update basic.c
Christy538 Oct 2, 2020
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17 changes: 15 additions & 2 deletions Basic_C_Examples/basic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -39,11 +39,24 @@ int main()

printf("Integer is %d\n", a); //print integer value
printf("Char is %c\n\n", b); //print character value



/*Takes the value entered by the user and displays the output*/
int i;
char h[20];
printf("Enter your name: \n");
scanf("%s",h); //Takes input from the user
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Using scanf like this is undefined behavior and can cause segfault or open up for malicious exploits. This will write the input to the stack until a word separator is found in the input, even if the input is longer than the size of the "h" buffer.

Use:
scanf("%19s", h); // leave 1 byte for the null-terminator

the rest of the line/word will be left in stdin and will be read by the next scanf instead of the number, so consider emptying stdin, e.g.

if (strlen(h) == sizeof(h)-1) while (getchar() != '\n'); // Empty left overs of name

printf("Your name is: %s\n",h);
printf("Enter a number: \n");
scanf("%d",&i);
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If the input number does not fit in an signed integer it will roll over, if it is not a number it will set i to 0. Some error handling for these cases are good practice, see https://wiki.sei.cmu.edu/confluence/display/c/INT05-C.+Do+not+use+input+functions+to+convert+character+data+if+they+cannot+handle+all+possible+inputs

printf("Entered number is %d\n",i);


/*Very Important!!! Characters are also integers, look at ASCII table*/
/*Another thing is chars are defined by ' ' not " ", strings are defined as " "*/

printf("Char is %c, integer "
printf("\nChar is %c, integer "
"value is %d\n\n", b, b); //print char and integer value

/*printf can print more variables read the documentation*/
Expand Down Expand Up @@ -98,4 +111,4 @@ int main()

getch(); //Standard function from stdio, wait for
return 0;
}
}