scanf and whitespaces

**cwr** · 03-03-2006

Originally Posted by WaltP

Alternatively:

Code:

char buf[20];
char clear[20];
int  len;

fgets(buf, 20, stdin);    // get a line
len = strlen(buf) - 1;    // last character's position
if (buf[len] == '\n')     // test for RETURN
{
    buf[len] = '\0';     // clear RETURN
}
else
{        // Too many characters were entered
    do   // read off the rest of the input buffer
    {
        fgets(clear, 20, stdin);  // get excess
        len = strlen(clear) - 1;
    }  while (clear[len] != '\n');
}

Consider what happens when EOF is sent with no characters. len is -1, because strlen(buf) is 0, and you get an infinite loop because there's no \n and the stream is EOF.

**WaltP** · 03-03-2006

Originally Posted by cwr

Consider what happens when EOF is sent with no characters. len is -1, because strlen(buf) is 0, and you get an infinite loop because there's no \n and the stream is EOF.

Good point... Although EOF is a little odd to enter from the keybord. Yes I know it's possible, but most users don't know how...

**Dave_Sinkula** · 03-03-2006

Originally Posted by WaltP

Good point... Although EOF is a little odd to enter from the keybord. Yes I know it's possible, but most users don't know how...

So don't forget to check for a successful call to fgets as well. And remember to consider piping.

**qqqqxxxx** · 03-06-2006

Code:

vehicle_make[strlen(vehicle_make)-1]='\0' ;

this is more than enough.

a newline character is considered a valid character and it can end the reading but in anycase A null character is always appended at the end of the resulting string.

if a newline is there vehicle_make[strlen(vehicle_make)-1] will contain the newline else it shall contain the default null character.

**Dave_Sinkula** · 03-06-2006

Originally Posted by qqqqxxxx

Code:

vehicle_make[strlen(vehicle_make)-1]='\0' ;

this is more than enough.

a newline character is considered a valid character and it can end the reading but in anycase A null character is always appended at the end of the resulting string.

if a newline is there vehicle_make[strlen(vehicle_make)-1] will contain the newline else it shall contain the default null character.

It's actually a little too much. If the newline isn't there, a non-null character will be there -- and you overwrite it anyway.

**quzah** · 03-06-2006

Didn't we already cover that? Since Prelude hasn't said anything, I'll steal this solution:

Code:

vehicle_make[ strspn( vehicle_make, "\n" ) ] = '\0';

Quzah.

**cwr** · 03-06-2006

Originally Posted by quzah

Didn't we already cover that? Since Prelude hasn't said anything, I'll steal this solution:

Code:

vehicle_make[ strspn( vehicle_make, "\n" ) ] = '\0';

Quzah.

You mean strcspn?

**quzah** · 03-06-2006

No, I meant strspn, which is why I used "\n". But that'll work too. :P (Actually I have never had occasion to use either one, which is why I never remember their names.)

Quzah.

**cwr** · 03-07-2006

The strspn() function calculates the length of the initial segment of s which consists entirely of characters in accept. So strspn("foo\n", "\n"); would return 0, since f is not \n.

**quzah** · 03-07-2006

Well that'll teach me (not really, but it should) to post tired. I read that backwards. Yeah, strcspn is what you want.

[edit]
I was thinking the pair of them were along the lines of strstr and its counterpart, strchr. Where one works with a string to search for, and one just searches for a single character.
[edit]

Quzah.

**rkooij** · 03-08-2006

Wow, haven't been here since I thought I had a working solution though I see there's been quite some uproar about this question

. I've replaced the 'strlen line' with the strcspn one as it seems to be a more watertight solution. Thanks again for all the help, good to see Quzah is also still learning

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