Input of multiple char arrays isn't working

Question

char toFind[100];
char replace[100];
int pos = 0;
printf("Enter a text: ");
scanf("%[^\n]", str);
printf("Enter a search pattern: ");
scanf("%[^\n]", toFind);
printf("Enter a substitute: ");
scanf("%[^\n]", replace);
pos = strnfnd(0, toFind);
strins(pos, replace);
printf("Der Text ist: %s", str);

This code sample let me read the value for str but skips the other two scanf. I have no idea why. What can I do to fix this?

Ps: str is a global char array

Answer 1

After this call of scanf

scanf("%[^\n]", str);

the new line character '\n' still is present in the input buffer.

So the next call of scanf

scanf("%[^\n]", toFind);

that reads input until the new line character '\n' is encountered reads nothing.

You should write for example

scanf("%[^\n]%*c", str);

to remove the new line character '\n' from the input buffer.

Here is a demonstration program

#include <stdio.h>

int main( void )
{
    char s[100];
    
    scanf( "%99[^\n]%*c", s );
    puts( s );
    
    scanf( "%99[^\n]", s );
    puts( s );

    return 0;
}

In this case if to enter strings for example like

Hello
      World

then the output will be

Hello
      World

Another and more simple approach is to prepend the format string with a blank. For example

scanf(" %[^\n]", toFind);
      ^^^^

In this case all leading white space characters will be skipped.

Here is a demonstration program.

#include <stdio.h>

int main( void )
{
    char s[100];
    
    scanf( "%99[^\n]", s );
    puts( s );
    
    scanf( " %99[^\n]", s );
    puts( s );

    return 0;
}

In this case if to enter strings as shown above that is

Hello
      World

then the program output will be

Hello
World