Removing newline.

Tarts · 10-16-2003, 07:06 AM

Is this sufficient to remove a newline when getting input from stdin with 'fgets()'?

Code:

if (fgets(password, strcspn(password, "\n"), stdin) == NULL) {
  reset_terminal();
  perror("fgets: input error, exiting\n");
  exit(-1);
}
reset_terminal();

Thank's, Tarts.

Hko · 10-16-2003, 12:44 PM

Quote:

Originally posted by Tarts

Code:

if (fgets(password, strcspn(password, "\n"), stdin) == NULL) { [...]

In this line strcspn() is called before fgets(), because when calling fgets(), the value for the second argument (int size) must be known, so strcspn() will be called to calculate where the newline is, after that fgets() is called with that value as an argument. This is the wrong order, because strcspn() uses the same string (char *password) as fgets() will write into. strcspn() is called first, so the input from stdin is not there yet.

As fgets() will puts exactly one newline at the end of the string it reads, I would first call fgets() to read the string from stdin, and then replace the last character of 'password' with '\0', so the newline will be replaced with the end-of-string marker '\0'. Like this:

Code:

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

#define MAXLEN 20

int main()
{
    char password[MAXLEN];

    printf("\nEnter a pasword: ");
    if (fgets(password, MAXLEN - 1, stdin) == NULL) {
	 fprintf(stderr, "Error fgets(), exiting...\n");
	 exit(EXIT_FAILURE);
    }
    password[strlen(password) - 1] = '\0';
    printf("\n\n ==> your password is:  %s\n\n", password);
    return 0;
}

Tarts · 10-16-2003, 12:49 PM

Quote:

Originally posted by Hko
In this line strcspn() is called before fgets(), because when calling fgets(), the value for the second argument (int size) must be known, so strcspn() will be called to calculate where the newline is, after that fgets() is called with that value as an argument. This is the wrong order, because strcspn() uses the same string (char *password) as fgets() will write into. strcspn() is called first, so the input from stdin is not there yet.

As fgets() will puts exactly one newline at the end of the string it reads, I would first call fgets() to read the string from stdin, and then replace the last character of 'password' with '\0', so the newline will be replaced with the end-of-string marker '\0'. Like this:

Thank you!

Tarts