fgets

[stautze]

I am using fgets like this:

  fp=fopen("test.txt","r"); //open file

  while(fgets(string,'\n',fp) != NULL){

    count++;

    if(strcmp(string, start) == 0){
      printf("%s found at line %d\n", string, count );
  }
    }

the problem is that I get the newline character too when I read each line of the file. I can't think of a good way to fix this.

Thanks in advance for any ideas.

[Vber]

char *fgets(char *s, size_t n, FILE *stream);

Ok, now the you have the prototype of the function, look at the second parameter, you should pass the size of the buffer, and not a char or everything else.

Also, when you open a file, check if you really opened it, if you haven't any error

if ((fp = fopen("file.txt","r")) == NULL) {
    perror("Fopen: ");
    return EXIT_FAILURE;
}

else {
    //you can use the file
}

[stautze]

my mistake, I just typed that out as an example of what I was doing, and I haven't coded in a while.... but I am using the correct parameters when I call fgets, I just wanted to know who you can get rid of the "\n".

[SourceCode]

Here is an example of how to eliminate a newline from an array.

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

int
main(void)
{
	
	char array[20];

	fgets(array, sizeof(array), stdin);
	
	/* If there is a '\n' we remove it */
	if (array[strlen(array)-1] == '\n') {
		array[strlen(array)-1] = '\0';
	}
	else { /* If there isn't one, we know there is garbage */
		while(getchar() != '\n'); 
	}


	return (0);
}

You could work with some variant of that, there are many more ways to remove newlines, many many more. For reading a file you could also read the file 1 character a time. Here is an example that removes every newline and stops reading at EOF, use Vbers example for checking if the file opened.

#include <stdio.h>

int
main(void)
{
	
	FILE *input;
	char data_line[BUFSIZ];
	int subscript;

	/* Open the file here and check for error like Vber showed */


	for (subscript = 0;(data_line[subscript] = fgetc(input)) != EOF; subscript++){
		if (data_line[subscript] == '\n') {
		    data_line[subscript] = '\0';
		}
	}
	return (0);
}

[stautze]

mahalo

[Vber]

actually fgets() leave an \n at the end of the buffer you're getting, always. You can use this code to remove the \n.

char *p;
p = strchr(buf,'\n');
if(p) *p = '\0';

Once there was a nice thread talking about removing the \n from fgets.

SourceCode wrote here some ways to do what you want

[Dave_Sinkula]

>actually fgets() leave an \n at the end of the buffer you're getting, always.

No, not always.

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

int main(void)
{
    char buffer[10];
    fputs("Prompt: ", stdout);
    fflush(stdout);
    if(fgets(buffer, sizeof(buffer), stdin) != NULL)
    {
        char *newline = strchr(buffer, '\n');
        if(newline != NULL)
        {
            puts("Found '\\n'. Replacing with '\\0'.");
            *newline = '\0';
        }
        else
        {
            int ch;
            puts("No '\\n' found. Eating excess characters:");
            do
            {
                ch = getchar();
                putchar(ch);
            } while(ch != '\n');
        }
        printf("buffer = \"%s\"\n", buffer);
    }
    return 0;
}

/* sample input/output
Prompt: text
Found '\n'. Replacing with '\0'.
buffer = "text"

Prompt: longer text
No '\n' found. Eating excess characters:
xt
buffer = "longer te"
*/

[Vber]

You're trying to show what? that you put a buffer of 10 and enter a long string, you expect the function to work well? what should I tell? Nice for you? always when fgets() buffer can take succefully the string, he will add \n, change the size of your buffer to 100 and check.

You're making something bad and expecting the function to works right, sorry, but this is kind stupid thing to do, use it with a proper buffer and he will add \n thats it.

Well, It's really clear to understand that if he haven't size to add \n he won't add... that's obvious, but one thing I don't understand, \0 he add always am I right?

[Hammer]

actually fgets() leave an \n at the end of the buffer you're getting, always.

It's really clear to understand that if he haven't size to add \n he won't add... that's obvious.

Your 2 sentences conflict each other, Dave was just pointing this out. And it's only obvious if you know the answer

Put simply, you cannot guarantee that a \n will be in the buffer, so blindly placing \0 over the last byte of the string is a bad thing to do. But you know this already, so why are we having this conversation..?

[edit]
>>\0 he add always am I right?
Yes, correct. \0 will always be present.

[Vber]

so blindly placing \0 over the last byte of the string is a bad thing to do

char *p;
p = strchr(buf,'\n');
if(p) *p = '\0';

This is not blindly, and this is from the thread you showed me once, about removing \n of fgets(), remember?

well, it's not needed to argue about this really
Thanks dave for showing this, I really didn't express myself correctly.

[Prelude]

>what should I tell? Nice for you?
No, you should thank him for informing you of your error. You should also not try to defend a mistake, if you do then you're the only one being fooled.

[edit]
>Thanks dave for showing this, I really didn't express myself correctly.
nevermind
[/edit]

>always when fgets() buffer can take succefully the string, he will add \n
Yes, but you didn't specify success previously, you said:

actually fgets() leave an \n at the end of the buffer you're getting, always.

Dave corrected you and showed you that your statement was not always true.

>You're making something bad and expecting the function to works right, sorry, but this is kind stupid thing to do
I disagree, you should attempt to break your code on purpose to make sure that it recovers or at least dies gracefully.

>use it with a proper buffer and he will add \n thats it.
A proper buffer being? char buffer[BUFSIZ]? I'm sorry, but no matter what size your buffer is, the chance is there that it will attempt to read a line that is too long.

-Prelude

[Vber]

No, you should thank him for informing you of your error. You should also not try to defend a mistake, if you do then you're the only one being fooled.

[edit]saw your post [/edit]

Yes, but you didn't specify success previously, you said:

I really didn't express myself correctly.

Dave corrected you and showed you that your statement was not always true.

And what I told him?
And what another thing I told here in the thread?

well, it's not needed to argue about this really

Well

[Heraclitus]

/* Create a "proper" buffer */
char string[640K_OUGHT_TO_BE_ENOUGH_FOR_ANYBODY];
fgets(string,sizeof(string),stdin);
strtok(string,"\n"); /* Will replace the first newline in string with a NULL */

[Dave_Sinkula]

One of the things I was trying to point out, and which was included in the code posted by SourceCode, was the handling of the case in which the input exceeds the buffer size. Text remains in stdin. Not handling it may be a bug, much like the issue with '\n' and scanf.

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

char *foo(char *buffer, size_t size, const char *prompt)
{
    if ( buffer != NULL )
    {
        if ( prompt != NULL )
        {
            fputs(prompt, stdout);
            fflush(stdout);
        }
        if ( fgets(buffer, size, stdin) != NULL )
        {
            char *newline = strchr(buffer, '\n');
            if ( newline != NULL )
            {
                *newline = '\0';
            }
#if 0
            else
            {
                while ( getchar() != '\n' ) { /* consume leftovers */ }
            }
#endif
        }
    }
    return buffer;
}

int main(void)
{
    char buffer[10] = "";
    while ( *buffer != '0' )
    {
        printf("buffer = \"%s\"\n", foo(buffer, sizeof(buffer), "prompt: "));
    }
    return 0;
}

/* sample input/output #if 0
prompt: This text is really, really, really long. Bigger than the buffer size.
buffer = "This text"
prompt: buffer = " is reall"
prompt: buffer = "y, really"
prompt: buffer = ", really "
prompt: buffer = "long. Big"
prompt: buffer = "ger than "
prompt: buffer = "the buffe"
prompt: buffer = "r size."
prompt: 0
buffer = "0"
*/

/* sample input/output #if 1
prompt: This text is really, really, really long. Bigger than the buffer size.
buffer = "This text"
prompt: 0
buffer = "0"
*/

Several searches show that I've left this out a number of times, so I thought it was worth menthioning.

[Prelude]

/* Create a "proper" buffer */
char string[640K_OUGHT_TO_BE_ENOUGH_FOR_ANYBODY];

Ooh, good one. Would be better if identifiers could begin with a digit.

-Prelude