Does anyone have an example of a conditional statement in C?

问题

Something like this, I'd like to see the full syntax.

Pseudo Code:

var = user_input

if var > 5:
    output = 'var > 5'
else:
    output = 'var < 5'

回答1:

How about something along the lines of:

#include <stdio.h>
#include <string.h>

int main (void) {
    int var;
    char buff[100];

    printf ("Enter number> ");
    fflush (stdout);
    if (fgets (buff, sizeof(buff), stdin) == NULL) {
        printf ("\nfgets() failed\n");
        return 1;
    }
    if (sscanf (buff, "%d", &var) != 1) {
        printf ("\nsscanf() failed\n");
        return 1;
    }

    if (var > 5)
        printf ("%d is greater than 5\n", var);
    else
        printf ("%d is less than 6\n", var);

    return 0;
}

with a couple of test runs:

pax> testprog
Enter number> 99
99 is greater than 5

pax> testprog
Enter number> -5
-5 is less than 6

回答2:

Variables and datatypes
Scanf
Conditional statements

Hope this will help you get started .

回答3:

This seems to correspond to what you'd like:

int var;
scanf("%d", &var);

if (var > 5)
    printf("var > 5\n");
else
    printf("var <= 5\n");

With caveats about using scanf() - I generally don't like it for resilient code, but it gives a minimal answer swiftly.

You'd have to wrap it in a main() and #include <stdio.h> to make it executable:

#include <stdio.h>
int main()
{
    int var;
    scanf("%d", &var);
    if (var > 5)
        printf("var > 5\n");
    else
        printf("var <= 5\n");
    return 0;
}

回答4:

In addition to the other two answers, there's always the ternary operator ?: which can be used like this:

printf("var %s 5\n", var > 5 ? ">" : "<=");

回答5:

if(condition)
    doThis();
else
    doThat();

It's pretty much what you've got there. Your example:

if(var > 5)
    output = "var > 5";
else
    output = "var < 5";

The only difference is that you need semicolons after the statements and parentheses around the conditional expression, and the colons are not required.

You can also use curly braces to denote a block of commands to execute given a certain condition. When there's only one line being executed, however, the braces are not necessary. But this is equivalent to:

if(var > 5)
{
    output = "var > 5";
}
else
{
    output = "var < 5";
}

You can have braces just after the if or just after the else, or both, or neither. Remember, though, that with multiple statements the braces are required.

It's also worth noting that the line breaks are optional. This could be written

if(var > 5) output = "var > 5";
else output = "var < 5";

Or even

if(var > 5) output = "var > 5"; else output = "var < 5";

But this code is far less readable. The first and second forms are better practice.

回答6:

char var = getchar();

if (atoi(var) > 5)
{
  printf("var > 5 \n");
}
else
{
  printf("var < 5 \n");
}

来源：https://stackoverflow.com/questions/3723658/does-anyone-have-an-example-of-a-conditional-statement-in-c

标签

conditional-statements