Length of a char array in C

Question

I want to calculate the length of an char array in C with a while loop. But If I insert otto it returns the length of 5. Shouldn't be 4 the right answer?

char eingabe[255];

printf("geben Sie eine Zeile ein:");
fgets(eingabe, 255, stdin);

int i = 0;
while (eingabe[i] != '\0')
{
    ++i;
}

printf("Laenge: %d\n", i);

It's probably counting a new line character (`\n`). Read `man fgets`. — , Nov 14 '14 at 13:48
`fgets` retains the new-line character at the end of the line, so you get 4 for "otto" plus one for that. — M Oehm, Nov 14 '14 at 13:48
Side note: when asking for help, have some consideration and write your code in English. It's not very important in this example, but with harder questions, it's a showstopper. — Filipe Gonçalves, Nov 14 '14 at 13:54

score 8 · Accepted Answer · answered Nov 14 '14 at 13:49

8

It's very likely that eingabe contains:

{ 'o', 't', 't', 'o', '\n', '\0', junk ... }

answered Nov 14 '14 at 13:49

Bill Lynch

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score 7 · Answer 2 · answered Nov 14 '14 at 13:50

Check the man page of fgets().

Reading stops after an EOF or a newline. If a newline is read, it is stored into the buffer.

As you are reading from stdin, it stores the trailing newline [\n] character also in the supplied buffer.

Change your check to while ((eingabe[i] != '\0') && (eingabe[i] != '\n')). Hope this will solve your issue.

score 1 · Answer 3 · answered Nov 14 '14 at 13:53

A newline character '\n' makes fgets stop reading, but it is considered a valid character by the function, and included in the string copied to the result. If you would like to avoid this, use fscanf like this:

fscanf(stdin, "%254[^\n]", eingabe);

Note the limit in the format: it is less than the actual length of the buffer to accommodate the null terminator.

Note: You can use strlen to compute the length of the string. It does the same thing as your for loop:

int i = strlen(eingabe);

score 0 · Answer 4 · answered Nov 14 '14 at 14:08

The size of eingabe is 255. Now, if you want the number of initialized characters in it you should use strlen. But first, insert this code:

int n;
for(n = 0; n < 255; n++){
  if(eingabe[n] == '\n'){
    eingabe[n] = '\0';
  }
}
eingabe[254] = '\0';

This code replaces the '\n' character with a NULL character. Without this, strlen will return wrong values. I also include eingabe[254] = '\0'; so that if the string read in is long enough that the newline character does not fit in the buffer, there is still a NULL character so that strlen can function properly

Length of a char array in C

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