Well I read input from user as:
scanf("%[^\n]", message);
And I initialise char message [100] =""; now, in another function I need to find out length of input in message, I did it easily with strlen(), unfortunately it doesn't work correctly when I do later in terminal
echo -e "he\0llo" | .asciiart 50
It will read the whole input BUT strlen will only return length 2.
Is there any other way I could find out length of input ?
By definition strlen stops on the null character
you have to count/read up to EOF and/or the newline rather than counting up to the null character after you read the string
As said in a remark %n allows to get the number of read characters, example :
#include <stdio.h>
int main()
{
char message[100] = { 0 };
int n;
if (scanf("%99[^\n]%n", message, &n) == 1)
printf("%d\n", n);
else
puts("empty line or EOF");
}
Compilations and executions :
pi@raspberrypi:/tmp $ gcc -g c.c
pi@raspberrypi:/tmp $ echo "" | ./a.out
empty line or EOF
pi@raspberrypi:/tmp $ echo -n "" | ./a.out
empty line or EOF
pi@raspberrypi:/tmp $ echo -e "he\0llo" | ./a.out
6
pi@raspberrypi:/tmp $
As you can see it is not possible to distinguish an empty line and EOF (even looking at errno)
You can also use ssize_t getline(char **lineptr, size_t *n, FILE *stream); :
#include <stdio.h>
#include <stdlib.h>
int main()
{
char *lineptr = NULL;
size_t n = 0;
ssize_t sz = getline(&lineptr, &n, stdin);
printf("%zd\n", sz);
free(lineptr);
}
but the possible newline is get and counted in that case :
pi@raspberrypi:/tmp $ gcc -pedantic -Wextra -g c.c
pi@raspberrypi:/tmp $ echo -e "he\0llo" | ./a.out
7
pi@raspberrypi:/tmp $ echo -e -n "he\0llo" | ./a.out
6
pi@raspberrypi:/tmp $ echo "" | ./a.out
1
pi@raspberrypi:/tmp $ echo -n "" | ./a.out
-1
