assert

Header file:

    assert.h

Synopsis:

     void assert(int expr);

Description:

     It aborts the program if the expr is false.

Sample program for assert in C:

---

  #include<stdio.h>
  #include<assert.h>
  #include<errno.h>
  int main() {
        FILE *fp;
        fp = fopen("jp.txt", "r");
        if (fp == NULL) {
                assert(fp);
        }

        printf("File opened in read mode\n");
        fclose(fp);
        return 0;
  }

  Output:

  jp@jp-VirtualBox:~/cpgms/assert$ ./a.out
  a.out: assert.c:8: main: Assertion `fp' failed.
  Aborted
  jp@jp-VirtualBox:~/cpgms/assert$ ls
  a.out  assert.c