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cstringnullcharterminator

Adding char with null terminator to string in C

What happens when in C I do something like:

char buf[50]="";
c = fgetc(file);
buf[strlen(buf)] = c+'\0';
buf[0] = '\0';

I'm using some this code in a loop and am finding old values in buf I just want to add c to buf

I am aware that I can do:

char s=[5];
s[0]=c;
s[1]='\0';
strcat(buf, s);

to add the char to buf, but I was wondering why the code above wasn't working.

Solution

  • This:

    buf[strlen(buf)] = c+'\0';

    will result to this:

    buf[strlen(buf)] = c;

    meaning that no addition will take place.

    Thus, what will happen is:

    buf[0] = c;

    since strlen(buf) is 0.

    This:

    buf[0] = '\0';

    puts a null terminator right on the start of the string, overriding c (which you just assigned to buf[0]). As a result it's reseting buf to "".