Question

I’m looking at some existing code and added a few printf lines. There’s a string cp “TZ=test”

cp = strchr(str, '=');
printf("Text: %s\n",cp);
printf("Text cp+1: %s\n",cp+1);
*cp = '\0';
printf("Text: %s\n",cp);
printf("Text cp+1: %s\n",cp+1);

the output is:

Text: =test
Text c+1: test
Text:
Text c+1: test

I understand the first two tests but why does the fourth one print “test” even though *cp was set to ‘\0’ right before?

Answer 1

Unlike some other languages, C doesn’t know what string is, it only knows where it ends, so it prints from the pointer that you give it.

    [=test\0]
1:   ^start here
          ^ end at \0
2:    ^start here
          ^ end at \0

    [\0test\0]
3:   ^start here, it's \0, so stop
4:     ^start here
           ^ end at \0